question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I have some data about music styles played at festivals. It looks like this:</p>
<p><img src="http://i.stack.imgur.com/SGXAa.png" alt="data"></p>
<p>Based on this (and other) data, I'd like to make a model to explain the price of a ticket for each festival. However I'm not sure how to handle this data in SPSS. Sho... | g64871 | [
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<p>Are multiple and multivariate regression really different? What <em>is</em> a variate anyways? :)</p> | g64872 | [
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<p>The features of my dataset are like below:<br>
<code>• BI-RADS assessment:</code> 1 to 5 (ordinal) <br>
<code>• Age:</code> patient's age in years (integer) ranges from 18 to 96<br>
<code>• Shape:</code> mass shape: round=1 oval=2 lobular=3 irregular=4 (nominal)<br>
<code>• Margin:</code> mass margin: circumscr... | g23216 | [
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<p>Let $X$ be a beta distributed variable with parameters $a$, $b$. Let $Y$ be a beta distributed variable with parameters $c$, $d$. Let $Z = \max(X, Y)$.</p>
<p>Does anybody know of a fast way to compute the mean and variance of $Z$ given $(a, b, c, d)$?</p>
<p>$X$, $Y$ don't necessarily need to have beta distributi... | g64873 | [
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<p>In his paper <a href="http://www.jstor.org/pss/2290328">Linear Model Selection by Cross-Validation</a>, Jun Shao shows that for the problem of variable selection in multivariate linear regression, the method of leave-one-out cross validation (LOOCV) is 'asymptotically inconsistent'. In plain English, it tends to sel... | g64874 | [
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<p>I am applying a random forest algorithm as a classifier on a microarray dataset which are split into two known groups with 1000s of features. After the initial run I look at the importance of the features and run the tree algorithm again with the 5, 10 and 20 most important features. <strong>I find that for all fe... | g37644 | [
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<p>Suppose for each sample S in training set TS I already know the k nearest neighbors.</p>
<p>The standard algorithms usually give S the same label as the majority of S's neighbors has.</p>
<p>What other use of nearest neighbors could I make? For instance, if I have not 3, not 5, but more neighbors, would it make se... | g64875 | [
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<p>A recent question on the difference between confidence and credible intervals led me to start re-reading Edwin Jaynes' article on that topic:</p>
<p>Jaynes, E. T., 1976. `Confidence Intervals vs Bayesian Intervals,' in Foundations of Probability Theory, Statistical Inference, and Statistical Theories of Science, W.... | g42977 | [
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<p>I was reading the book <a href="http://www-stat.stanford.edu/~tibs/ElemStatLearn/" rel="nofollow">Elements of Statistical Learning</a> and came across the section that tried to interpret ridge regression using singular value decomposition (SVD) of the design matrix, $X$. Specifically, I found the following:</p>
<p>... | g64876 | [
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<p>I want to integrate
$\int_{\mathbb{R}_+}\mathbb{1}_A(x) d\mathbb{P}(x)$, in other words I am interested in $\mathbb{P}(A)$. I did this numerically with two Monte Carlo steps. </p>
<p>First, I drew, say a sample of $10^3$ ($\mathbb{P}$-distributed). From this sample I calculated the mean. Repeating this $N$ times, i... | g64877 | [
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<p>If we know, for independent random variables $X$ and $Y$,
$P(X>x)\leq0.05$, and $P(Y>y)\leq0.05$, can we say anything about $P(X+Y>x+y)$? Can we be certain that it is less than $0.05$? Under what conditions could we say that?</p> | g42980 | [
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<p>Can I compare outcome data from different literacy measures with different scales (delivered to different subjects) by transforming the data into z scores? Ideally I'd like to use regression and ANOVA techniques to determine if there are significant differences between groups that got different types of literacy in... | g64878 | [
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<p>I have a data set that is broken into the four categories, each with four data points. I am asked to compare the confidence limits of the four categories. How do I go about doing this?</p>
<p>I know to create confidence limits you need t tests, however they only compare two means, not four.</p> | g64879 | [
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<p>I am currently analysing some pretty awful/awkward data on the abundance of fish under three different "Hydro-Regimes" (5 abundance measurements for each regime - Short/Medium/Long). The current analysis plan had been a one way ANOVA.</p>
<p>Looking at the residuals vs. fitted and the normal Q-Q after plugging it i... | g64880 | [
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<p>I have a very beginner's question regarding the Central Limit Theorem (CLT):</p>
<p>I am aware that the CLT states that a mean of i.i.d. random variables is approximately normal distributed (for $n \to \infty$, where $n$ is the index of the summands) or the standardized random variable would have a standard normal ... | g42986 | [
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<p>I have a software benchmark which is quite noisy. I am trying to for the bugs which are causing the noise, and I need to be able to measure it somehow.</p>
<p>The benchmark is comprised of a number of subbenchmarks, for example:</p>
<pre><code>"3d-cube": 31.56884765625,
"3d-morph": 21.89599609375,
"3d-raytrace": 5... | g64881 | [
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0.1... |
<p>Assume that we want to extract information from a constantly updating table like stock trading volume, where a banker can buy or sell at specific price. The table has the following 4 columns: price, available, traded, buy/sell.</p>
<p>The fist column gives the price that the amount given by the 2nd column is availa... | g23228 | [
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<p>I have encountered the following integral:
$$
\int_{- \infty}^{+ \infty} X(\theta) \frac{\exp \big \{-\frac{\theta^2}{2\sigma^2} \big \}}{\sigma\sqrt{2 \pi}}d\theta
$$
where, for fixed $\theta = \theta_0$, $X(\theta_0) \sim N(0, 1)$. $X(\theta_1)$ and $X(\theta_2)$ are independent if $\theta_1 \neq \theta_2$. Hence ... | g23231 | [
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<p>I am wondering if anyone has insight regarding the creation of interaction terms (moderators) in a model with latent predictors using Stata 13 - SEM. I have what I want to be the moderator set up currently as a mediator and need to test competing models. I am not sure if I need to run a multiple group model or if th... | g64882 | [
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<p>Why is direct sampling from the posterior distribution intractable?</p> | g23232 | [
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<p>I have tried to read about tangent propagation in neural networks (although I guess it could be applicable to other methods) which is a procedure to create models that are invariant to certain transformation. So basically the argument goes like this:</p>
<p>Start with an input vector $x_{n}$. Then use a linear tran... | g42998 | [
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<p>I've been trying to aggregate <em>correlated</em> time series, by using Alexander's proposal that you can see here: <a href="http://bit.ly/1hIPwiI" rel="nofollow">http://bit.ly/1hIPwiI</a>.</p>
<p>Her proposal to find a random variable $Y=\sum_{i=1}^N X_i$, where each $X_i$ represents a stochastic process, is based... | g64883 | [
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<p>I'm running a binary logistic regressions with 3 numerical variables. I'm suppressing the intercept in my models as the probability should be zero if all input variables are zero.</p>
<p>What's minimal number of observations I should use?</p> | g23235 | [
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<p>I have a JAGS hierarchical model which includes a temporal sub-model for the primary vote share between four party groups (LNP, Labor, Green, and Other). For each day in the temporal model, the vote shares sum to one. The temporal model is an auto-regressive random walk: the vote shares for the four party groups tod... | g37554 | [
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<p>Repeating an experiment (<a href="http://stats.stackexchange.com/questions/10407/probability-for-finding-a-double-as-likely-event">about which I asked before</a>) with $n$ possible outcomes $t$ times independently, where all but one outcomes have probability $\frac{1}{n+1}$ and the other outcome has the double proba... | g23237 | [
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<p>I'm quite new to this, but I have geographical data and I want to calculate latitudinal shifts.
I have in each row a minimum, maximum, median, average and standard deviation of latitude BEFORE 1980. In the same row, I have the same variables but from AFTER 1980.
Goal is to select the rows that have trustworthy value... | g64884 | [
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<ol>
<li>It was mentioned that Volume 2 of Mathematical Statistics by Bickel
and Doksum was scheduled to be published in 2003. I was wondering
if I miss something, but why it is not yet available? Is there some
change of plan?</li>
<li>Volume 1 of Robust Asymptotic Statistics by Helmut Rieder was
published in 90's. B... | g23240 | [
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<p>I have a survey with 25 items that were administered pre and post an intervention. Each item had four possible responses: </p>
<ul>
<li>Not Appealing at all</li>
<li>Not Appealing</li>
<li>Somewhat Appealing</li>
<li>Very Appealing.</li>
</ul>
<p>The survey was given to a class of 60 students. I have entered the d... | g43000 | [
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<p>I am maximizing the log-likelihood function for a generalized linear model without using per-written functions like <code>glm</code> due to the form of the model I have. So to maximize the log-likelihood, I am using the <code>optim</code> function. That works fine. But how can I double check if the estimated paramet... | g64885 | [
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<p>I'm trying to fit a Dirichlet process Gaussian mixture model to 2-D data using a stick-breaking prior. I have a normal-inverse Wishart prior on my cluster means and covariances, where $$\{\mathbf{\mu_i}, \mathbf{\Sigma_i}\} \sim \mathcal{N}\mbox{IW}(\mathbf{\theta_0}, \lambda_0, \mathbf{\Sigma_0}, \nu_0) \leftrighta... | g64886 | [
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<p>I am new to profile likelihood and do not really understand what advantages it may have. Lets say I have the following results estimating the means of three groups. What can I say about them?</p>
<p><img src="http://i.stack.imgur.com/1USWx.png" alt="enter image description here"></p>
<p><strong>R code:</strong></p... | g30371 | [
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0.11077052354812622,
-0.019756516441702843,
-0.059731971472501755,
-0.009788310155272484,
-0.032641150057315826,
0.007653800770640373,
0.03403659164905548,
... |
<p>The Wikipedia entry on Mahalanobis Distance contains this note: </p>
<blockquote>
<p>Another intuitive description of Mahalanobis distance is that it is square root of the negative log likelihood. That is, the exponential of the negative square of the Mahalanobis distance will give you the likelihood of your dat... | g64887 | [
0.06255137920379639,
0.0056701535359025,
-0.007508403621613979,
-0.005635538604110479,
-0.005732540041208267,
-0.00014875778288114816,
0.04332524910569191,
0.06258759647607803,
-0.024965712800621986,
0.0014311609556898475,
-0.011893600225448608,
0.03233935311436653,
0.06143301725387573,
-0... |
<p><strong>Question 1 (part 1)</strong></p>
<p>I was attempting to use the exponential distribution to solve the following problem:</p>
<blockquote>
<p>the time between cars passing on a road can be modelled with an avg rate of 3.5 cars per minute. Find the probability that the time between two comsecutive cars pas... | g23246 | [
0.03781510889530182,
-0.002212453866377473,
0.008274354971945286,
-0.04789618030190468,
0.03429136052727699,
-0.04060686379671097,
0.03506653010845184,
-0.03605886548757553,
-0.040789443999528885,
0.04138505831360817,
0.017671547830104828,
-0.020890936255455017,
0.025671228766441345,
0.003... |
<p>I got a weird result with linear regression: there are empty significances. I use 'Stepwise' method, so it should drop the inadequate variables. (Of course the "000" Betas are confusing too.)</p>
<p>What could be the reason, and what should be the solution?</p>
<p>Thank you very much in advance.</p>
<p><img src="... | g64888 | [
0.0008071205229498446,
-0.02796759642660618,
-0.006033335812389851,
-0.06924807280302048,
0.05626795068383217,
0.02608831413090229,
0.024210110306739807,
0.026883460581302643,
-0.03324981406331062,
-0.04307661950588226,
-0.05047669634222984,
0.020131981000304222,
0.023742901161313057,
0.08... |
<p>The data I am using can be found here: <a href="http://uploadeasy.net/upload/nwv0.rar" rel="nofollow">http://uploadeasy.net/upload/nwv0.rar</a>
The variable is called "alvsloss".</p>
<p>I want to fit a distribution to my financial data. First of all, I started with a normal distribution.</p>
<p>The pdf is given by... | g49382 | [
0.015778319910168648,
-0.04279008507728577,
-0.03214140608906746,
-0.05689626932144165,
0.0004921904765069485,
0.017702557146549225,
0.024781934916973114,
-0.03478221222758293,
-0.08611256629228592,
-0.00831691361963749,
-0.038196712732315063,
0.03629760816693306,
0.05858548358082771,
-0.0... |
<p>I have collected some gene expression data and I want to learn a Bayesian network out of it.
Before that, I want to do some statistical analysis to test the quality of my data.
Now I want to know that, which kind of statistical analysis I should do to assess the quality of my data?</p> | g64889 | [
0.027452033013105392,
0.0006114906282164156,
0.0032344013452529907,
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0.0036990437656641006,
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0.013685676269233227,
0.049156539142131805,
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-0.03958806023001671,
0.0065870340913534164,
0.057118166238069534,
0.019752606749534607,
... |
<p>I have a dataset with two factors <code>A</code> and <code>B</code> and the following design (contigency table showing the number of individuals for each crossed level):</p>
<pre><code>> xtabs(~A+B, data=dd2)
B
A B1 B2 B3 B4
A1 8 8 8 8
A2 7 7 7 7
A3 8 8 8 8
A4 4 4 4 4
A5 4 4 4... | g23249 | [
-0.010888859629631042,
0.029737677425146103,
-0.004108357708901167,
-0.027579018846154213,
0.008908962830901146,
0.0027820435352623463,
0.05261189118027687,
0.0006381611456163228,
0.0033208474051207304,
-0.0009303027181886137,
-0.03566551208496094,
-0.0008572565857321024,
-0.0037659297231584... |
<p>I am not a statistician, so go easy on me here...</p>
<p>I have collected lots of data on the behaviour of customers in a shop. A customer will enter the shop and a series of events will then take place (eg look at product, look at advert in shop, talk to shop assistant, etc). Before they leave the shop, some cus... | g64890 | [
-0.030148297548294067,
0.02787856012582779,
-0.0151923643425107,
-0.012736027128994465,
-0.042481228709220886,
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0.09853309392929077,
0.022899096831679344,
0.041614945977926254,
-0.04630722478032112,
0.013355782255530357,
0.014830470085144043,
0.07711462676525116,
0.01... |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/16968/computing-per-cent-correctness-from-a-bell-curve">Computing per cent correctness from a bell curve</a> </p>
</blockquote>
<p>I've been trying to remember my High School teachings and are falling shor... | g49708 | [
0.06739668548107147,
-0.055877480655908585,
0.011736488901078701,
-0.048425737768411636,
0.009156777523458004,
-0.04642285779118538,
0.026624461635947227,
-0.021535290405154228,
-0.024059653282165527,
0.024748552590608597,
0.010145905427634716,
0.0774863138794899,
0.03826695308089256,
-0.0... |
<p>I have a folder for each class that contains some text files related to that class and need to implement a classifier for these files in RapidMiner with KNN algorithm.</p>
<p>Is there any sample?</p> | g37806 | [
-0.0018792900955304503,
-0.04886980354785919,
0.014091762714087963,
0.00454080943018198,
-0.024079037830233574,
-0.061027348041534424,
-0.05029229447245598,
0.03907721862196922,
-0.08458194136619568,
-0.001751263509504497,
0.0075068664737045765,
0.0005475025973282754,
0.01883598044514656,
... |
<p>Suppose we have the following dataset that records individual survival times (dur) and a covariate z: </p>
<pre><code>id| dur | z
-------------
1 | 1 | -1
2 | 2 | 1
3 | 3 | -1
4 | 4 | 1
</code></pre>
<p>I want to model the duration as a function of z. I may specify dur ~ weibull() and parameterize the sc... | g43018 | [
-0.007313958834856749,
-0.017482465133070946,
-0.02344043180346489,
-0.0584634393453598,
0.014737405814230442,
-0.036858074367046356,
0.04477914050221443,
-0.029778197407722473,
-0.08789408951997757,
0.01944313570857048,
-0.01780092716217041,
0.009559380821883678,
0.038541827350854874,
0.0... |
<p>I know the definition, but what does it imply if one estimator has greater coverage probability than another estimator? Does it imply that it has converges to the parameter of interest faster?</p> | g64891 | [
0.08741635084152222,
0.0334327407181263,
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0.025373980402946472,
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0.016320472583174706,
0.011682451702654362,
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-0.00833947118371725,
-0.04480881989002228,
0.009874070063233376,
0.032827332615852356,
0.02280... |
<p>I have data on a large Italian firm's employees over ten years and I would like to see how the gender gap in male-female earnings has changed over time. For this purpose I run pooled OLS:
$$
y_{it} = X'_{it}\beta + \delta {\rm male}_i + \sum^{10}_{t=1}\gamma_t d_t + \varepsilon_{it}
$$
where $y$ is log earnings per ... | g64892 | [
-0.010713472031056881,
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0.0036794201005250216,
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0.01160070113837719,
0.05448247864842415,
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-0.00031485495856031775,
-0.011635519564151764,
0.05670598894357681,
0.02400757186114788,
... |
<p>I have run LMM models with different reference categories and this yield different results: </p>
<pre><code>> summary(lmer3)
Linear mixed model fit by maximum likelihood ['merModLmerTest']
Formula: v000001 ~ (1 | item) + (1 + color | speaker) + Language * color * sex
Data: data1.frame
AIC ... | g64893 | [
0.005363114643841982,
-0.07207785546779633,
0.01951763406395912,
-0.047075025737285614,
0.03361937776207924,
0.027089787647128105,
0.038193684071302414,
-0.023427346721291542,
-0.05121421813964844,
0.006529523991048336,
-0.005264847539365292,
0.010248505510389805,
0.031922634690999985,
0.0... |
<p>When solving <a href="http://www.euroviakamenolomy.cz/dokumenty/verejne/Casopis/Pictures/sk070123.gif" rel="nofollow">crosswords</a> today, I thought of if they can be generated automatically by any mathematical approach. </p>
<p>My question is: If database of words and any grid with some cells already filled (solu... | g64894 | [
0.03131571039557457,
0.01245743129402399,
0.020628349855542183,
-0.02965366095304489,
0.021283594891428947,
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0.008747737854719162,
0.05695835500955582,
-0.090358667075634,
0.05656115338206291,
-0.033174920827150345,
-0.030699746683239937,
0.03438789024949074,
0.046557... |
<p>I am studying a parameter in several organs of mice and I have two categorial factors. I would like to study the effects of those two factors on my parameter in each organ (I don't care about differences of the parameter bewteen organs). I was previously doing a two-way ANOVA for each organ but this led to multiple ... | g23255 | [
-0.044933490455150604,
-0.012926441617310047,
0.014379827305674553,
-0.021313326433300972,
-0.046830590814352036,
0.01370998378843069,
-0.035099953413009644,
0.015484035015106201,
-0.04061700776219368,
0.021483218297362328,
-0.02437504380941391,
0.06900595128536224,
-0.05578997731208801,
0... |
<p>I'm working with a large data set (confidential, so I can't share too much), and came to the conclusion a negative binomial regression would be necessary. I've never done a glm regression before, and I can't find any clear information about what the assumptions are. Are they the same for MLR? </p>
<p>Can I transfor... | g64895 | [
-0.002423893893137574,
-0.0007011247798800468,
-0.012584343552589417,
0.021052734926342964,
-0.04273950681090355,
-0.006664926186203957,
-0.02616153657436371,
-0.025517676025629044,
-0.08346857130527496,
-0.06517136096954346,
-0.010433311574161053,
0.01639707386493683,
0.04492931067943573,
... |
<p>Is there a possibility to use R in a webinterface without the need to install it?</p>
<p>I have only one small script which I like to run but I just want to give it a shot without a long installation procedure.</p>
<p>Thank you.</p> | g64896 | [
0.02472003549337387,
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0.0089033804833889,
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0.04980332776904106,
-0.011373321525752544,
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-0.07110794633626938,
-0.011078998446464539,
0.03567839786410332,
-0.03498665243387222,
0.056039... |
<p>I've been struggling with this problem for a couple of hours, and I could use some advice.</p>
<p>I have a linear regression model with two continuous predictors and a categorical one (with 4 levels). I want to test for a linear trend in the categorical variable, with the lowest level as the reference. I've gotten ... | g24892 | [
0.017765717580914497,
-0.052058786153793335,
-0.000880027306266129,
-0.018375763669610023,
0.03854770213365555,
-0.022433189675211906,
0.006056707352399826,
0.01991480216383934,
-0.07029940187931061,
-0.016183264553546906,
-0.010383406654000282,
0.03727222606539726,
0.04466653987765312,
0.... |
<p>Let $X_1,...,X_n$ be iid with pdf</p>
<p>$$f(x|\theta) = exp(\theta -x) I(x)_{(\theta, \infty)}$$</p>
<p>It is asked to find an unbiased estimator for$ \theta $ that is function of a sufficient statistical for $\theta$</p>
<p>By factorization theorem, we show that $X_{(1)}$ is a sufficient statistical for $\theta... | g64897 | [
0.011763893067836761,
0.017308739945292473,
-0.0058664483949542046,
0.0018942096503451467,
0.06675007194280624,
-0.054470244795084,
0.041443075984716415,
0.01917361468076706,
-0.014279322698712349,
0.040403030812740326,
0.04050462692975998,
0.021371634677052498,
-0.011147312819957733,
0.00... |
<p>I have a plot like this. </p>
<p><img src="http://i.stack.imgur.com/bru73.png" alt="enter image description here"></p>
<p>I wish to apply a model to this, however, I guess a linear regression model won't work on this. What I did was plot it on logarithm x and logarithm y axis as well but it came out to be of no us... | g64898 | [
-0.0029915787745267153,
-0.01803271286189556,
0.009631778113543987,
-0.047354742884635925,
-0.04573005810379982,
-0.024366088211536407,
0.002099778037518263,
0.024515433236956596,
-0.025063317269086838,
-0.04327179491519928,
0.023393986746668816,
-0.008977075107395649,
0.016835549846291542,
... |
<p>In <a href="http://projecteuclid.org/DPubS?verb=Display&version=1.0&service=UI&handle=euclid.ss/1009213726&page=record">Statistical Modeling: The Two Cultures</a> Leo Breiman writes </p>
<blockquote>
<p>Current applied practice is to check
the data model fit using
goodness-of-fit tests and res... | g43024 | [
0.04161861166357994,
0.012063512578606606,
0.000042615345591912046,
0.005518265534192324,
-0.00895489752292633,
-0.011961064301431179,
0.01534061599522829,
0.008224913850426674,
-0.050241339951753616,
-0.0026962789706885815,
0.006620698608458042,
-0.014864752069115639,
0.015956666320562363,
... |
<p>In a (one or multi) way anova model, once a new individual is assigned to a treatment, the predicted value for him is calculated using the coefficients of the ANOVA model (simply assigning the treatment mean value to the individual). </p>
<p>How should I construct a confidence (or prediction) interval for that pred... | g64899 | [
-0.03373497352004051,
-0.04662887752056122,
-0.006412168499082327,
0.005851371213793755,
-0.014114338904619217,
0.011972394771873951,
0.008972072042524815,
0.01942465268075466,
-0.014903100207448006,
0.0065465690568089485,
-0.040724530816078186,
0.04334205016493797,
0.036884184926748276,
-... |
<p>What are some hot topics that mathematical statistics researchers are studying now?</p> | g64900 | [
0.06906197220087051,
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0.01611911505460739,
0.007110136561095715,
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-0.06482283771038055,
-0.0027344748377799988,
0.03196649253368378,
0.06623843312263489,
0.01... |
<p>As a follow up to my <a href="http://stats.stackexchange.com/questions/9629/can-chi-square-be-used-to-compare-proportions">previous question</a>, I learned that the chi square test can be used to compare expected and observed frequency distributions. But...</p>
<p>Suppose I have the following data table in CSV, whi... | g64901 | [
-0.010245800949633121,
-0.0007714445819146931,
0.018506476655602455,
-0.050455085933208466,
-0.012965304777026176,
-0.03379705548286438,
0.004405423533171415,
0.0398886576294899,
0.00741197494789958,
0.002015609061345458,
0.005933289881795645,
-0.001974897924810648,
0.04689977690577507,
-0... |
<p>When predicting the value of a response variable from the value of an explanatory variable, if I am correct, </p>
<ul>
<li>when the response is real-valued, the task is regression, and </li>
<li>when the response takes values from a unordered discrete set, the task is classification.</li>
</ul>
<p>When the respons... | g64902 | [
0.03647730126976967,
0.018537091091275215,
-0.0011706138029694557,
-0.09421343356370926,
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-0.04783611372113228,
-0.0156319011002779,
-0.0019329620990902185,
-0.013676964677870274,
-0.09562254697084427,
-0.019375452771782875,
0.007724118418991566,
0.030344458296895027,
... |
<p>For a research project I need to find the expected value of the generalized Rayleigh quotient:
$$E\,[w^T A w \ / \ w^T B w].$$ Here <em>A</em> and <em>B</em> are positive definite deterministic <em>p</em> x <em>p</em> covariance matrices, and <em>w</em> follows a multivariate distribution with circular altitude line... | g23260 | [
0.0012841079151257873,
-0.055420517921447754,
-0.034552086144685745,
-0.011583256535232067,
-0.03676871210336685,
0.018032392486929893,
0.004326613619923592,
-0.040315333753824234,
-0.004178020171821117,
0.022611306980252266,
0.046892452985048294,
0.012107327580451965,
-0.008626646362245083,... |
<p>I have a training set which is complete - no missing values, but yet if I pretty print one of the trees in gbm I see that the algorithm has determined a strategy for missing data. This is smarter than I thought it would be, because in the future the data may not always be complete. I'm wondering if the tree just t... | g64903 | [
-0.006556810345500708,
-0.033490363508462906,
-0.00015972454275470227,
-0.025257470086216927,
0.0366705060005188,
-0.0007383291958831251,
0.0375322662293911,
0.004571372643113136,
-0.019765716046094894,
-0.02664905972778797,
-0.02493993565440178,
0.012757168151438236,
-0.011287648230791092,
... |
<p>I am using JAGS to estimate a Dirichlet Process Mixture of Normals. The code works well and the estimated density is accurate. However, I would like to know which component each observation is assigned to and the corresponding parameters for that component. This is hard due to the label switching problem in mixtu... | g23261 | [
-0.06066358461976051,
-0.03991085663437843,
-0.011794696561992168,
-0.10585811734199524,
-0.013073845766484737,
-0.04880195111036301,
0.04634092375636101,
-0.012992453761398792,
-0.04515644907951355,
-0.011094499379396439,
0.02284620888531208,
0.04927641898393631,
0.05899061635136604,
0.03... |
<p>I apologize if this is a basic question - I'm a complete beginner with machine learning & stats.</p>
<p>I am working on a website where signing up for a premium feature requires the user to fill out a questionnaire prior to adding the premium. So I have a dataset of:</p>
<ol>
<li>Users who completed the quest... | g64904 | [
-0.0348382294178009,
0.04527479410171509,
0.004293971229344606,
-0.013224083930253983,
0.04202788323163986,
-0.024562301114201546,
-0.0022362673189491034,
0.018623175099492073,
0.015038404613733292,
-0.021047266200184822,
-0.011785509996116161,
-0.0009684776305221021,
0.07209528982639313,
... |
<p>I have one group of participants measured on a health outcome scale at two different time points. I first want to see whether there is a significant difference between time 1 and time 2 on this outcome variable, I then want to see if this outcome variable at T2 is predicted by another dimensional variable (BPD dimen... | g23262 | [
-0.00932842493057251,
-0.06280160695314407,
-0.0010317821288481355,
-0.05332666635513306,
-0.027017179876565933,
-0.01708383299410343,
0.04475397244095802,
0.008633427321910858,
-0.03728364408016205,
-0.0005347620462998748,
0.030311016365885735,
0.01412118785083294,
0.018445923924446106,
0... |
<p>I am struggling to make the mathematical connection between a neural network and a graphical model.</p>
<p>In graphical models the idea is simple: the probability distribution factorizes according to the cliques in the graph, with the potentials usually being of the exponential family.</p>
<p>Is there an equivalen... | g43030 | [
0.02916789799928665,
-0.003828126937150955,
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-0.02267986163496971,
0.06701429933309555,
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0.08009564131498337,
0.0267... |
<p>In SVM, there is a bias term. But looks to me there are very few discussions on the physical meanings of this term. Why should we have that? How does this term affect the model?</p> | g37570 | [
0.018566301092505455,
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<p>I have a simulated data set and I want to fit a "smooth approximation line" like the image I have provided. </p>
<p><img src="http://i.stack.imgur.com/aPE28.jpg" alt="http://i1024.photobucket.com/albums/y307/sarmadys/fitting_zps9d9651e7.jpg (I did not have enough rep to post image)"></p>
<p>1- Is it possible to d... | g45835 | [
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<p>I have # of students consenting to be vaccinated and # of students eligible to be vaccinated for 77 schools in three school years (2010/11, 2011/12, and 2012/13). Between 2011/12 and 2012/13 there was an intervention to increase consent rates. I want to be able to model (with a repeated measures model) the change in... | g64905 | [
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<p>I want to build a machine learning model to regression on continuous output given binary valued features(0,1). the dimension of my problem is around 200. which of the flowing methods seems suitable for this kind of problem ?</p>
<p>SVR with different Kernels</p>
<p>Regression random forest</p>
<p>MARS</p>
<p>Gra... | g40579 | [
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<p>I would like some advice on how to implement a Kolmogorov-Smirnov test.</p>
<p><strong>This is a condensed version of my previous question -- any further detail can be provided if needed.</strong></p>
<p>I have data from <em>n</em> experimental trials. Each set consists of two paired time-series signals, for which... | g64906 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/346/what-is-a-good-algorithm-for-estimating-the-median-of-a-huge-read-once-data-set">What is a good algorithm for estimating the median of a huge read-once data set?</a> </p>
</blockquote>
<p>Imagine you h... | g49709 | [
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<p>Suppose we have three independent normally distributed random variables
$$ X_0 \sim \mathcal{N}(\mu_0, \sigma_0^2), $$
$$ X_1 \sim \mathcal{N}(\mu_1, \sigma_1^2), $$
$$ X_2 \sim \mathcal{N}(\mu_2, \sigma_2^2).$$</p>
<p>Now, define two new random variables $Y_0 = X_0+X_1$ and $Y_1 = X_1+X_2$. </p>
<p>Let $\vec{Y}... | g37672 | [
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0... |
<p><img src="http://i.stack.imgur.com/4IGUc.jpg" alt="http://i.stack.imgur.com/jGUjB.jpg"></p>
<p>Sorry for the game-image link, I've wondered what this diamond-shaped graph is called for some time, any idea what type of chart/graph this is?</p> | g24934 | [
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<p>Is it possible to determine if distribution of time-series has shifted significantly without assuming any particular underlying data distribution? </p>
<p>Furthermore, would it be possible to identify point of split between (possibly two) distributions?</p>
<p>Any links to softwares or pointers to references wou... | g23270 | [
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<p>I have a process with binary output. Is there a standard way to test if it is a Bernoulli process? The problem translates to checking if every trial is independent of the previous trials.</p>
<p>I have observed some processes where a result "sticks" for a number of trials.</p> | g64907 | [
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<p>I've been struggling with how to think about the causal estimate of a program on two outcomes, when one of the two outcomes affects the other outcome. It seems sort of like simultaneous equations, but reading up on SEM, I don't see immediately how it could apply. Would appreciate any ideas for how to approach this... | g64908 | [
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<p>What is the best way to deal with correlated regressors? </p>
<p>I am running a regression with No. of Accidents as the Dependent Variable and Traffic Flow and Speed as the independent variables.</p>
<p>The problem I have is that obviously Flow and Speed are related as when flow decreases, speed increases. This is... | g49710 | [
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<p>I want to estimate a nonlinear coefficient from a 2 equations system and use the delta method to calculate the standard errors for inference.</p>
<p>\begin{align}
y_{i1} &= \alpha_{0} + \alpha_{1}x_{i}+\alpha_{2}y_{i2}+\varepsilon_{i1} \\
y_{i2} &= \beta_{0} + \beta_{1}x_{i}+\beta_{2}z_i+\varepsilon_{i2} ... | g510 | [
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<p>Questions regarding factor analysis and principal component analysis, both here and elsewhere, reveal considerable confusion of terms, disagreements about requirements, different recommendations for different issues and so on. Different programs label the same output differently. There is a fairly bewildering numbe... | g23271 | [
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<p>I am trying to derive some probabilities from the following graphical model and I am having some difficulty. The model is actually a complete bipartite graph with two sets of nodes C and W. The graph is a directed graph where each $c_i$ connects to each $w_i$. That is all of the connections.</p>
<p>I am interested ... | g64909 | [
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<p>Consider a Wilcoxon-Mann-Whitney test statistic, either in the form </p>
<p>(i) "W = sum of ranks in sample A"; or in the form </p>
<p>(ii) "sum of ranks in sample A - the minimum possible sum of ranks in sample A", or equivalently "U = the number of times a value in sample 1 exceeds a value in sample 2".</p>
<p>... | g23273 | [
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<p>I have some questions about specifying a <code>coxme</code> (mixed-effects Cox proportional hazards) model in R and then simplifying it after reading the <code>coxme</code> documentation. The situation is this:</p>
<p>I glued 4 pieces of small coral fragments onto small ceramic tiles, which I placed at 4 distances ... | g64910 | [
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<p>As a part of a project for the university is should train a Naive Bayes classifier to classify question and answers in three different categories, the task should be easy since that the 3 classes are really different between each other.</p>
<p><strong>Dataset</strong></p>
<p>the dataset is a mixture of questions a... | g64911 | [
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<p>I am currently working on a data mining project during an in internship, and I use among others methods decision trees.
My problem is that I have a categorical predictor very influent on classification, but I want to ignore this influence to better analyze the behaviour of other predictors.</p>
<p>I could of course... | g64912 | [
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<p>How to sample from a multivariate normal given the $P^TLDL^TP$ decomposition of $\Sigma$, and $\mu$?</p>
<p>Here, $P$ is a permutation matrix, $L$ is lower-triangular, and $D$ is diagonal</p>
<p>Given the Cholesky decomposition $LL^T$ of $\Sigma$, and $\mu$, we can sample by doing:</p>
<p>$sample = \mu + L * z$</... | g64913 | [
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<p>I had an interesting exam question yesterday, in which you had the outcomes of number people killed in traffic accidents in two subsequent years (the second being relatively higher than the first). Now you should calculate the <strong>exact p-value</strong> for the hypothesis that the second outcome was due to a cha... | g64914 | [
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<p>I am considering the Inverse Gaussian distribution as the hitting time distribution for a Wiener process, $W(t)$, with drift parameter $\nu$ and variance parameter $\sigma$. Define the hitting time as the first time the process reaches the level $a > 0$: </p>
<p>$T = \min_{t>0}\{ W(t) \geq a\}.$ </p>
<p>The ... | g23276 | [
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<p>From a larger sample of tabular data, I have picked certain rows that meet a certain condition (this condition is unrelated to the actual data in the rows).</p>
<p>Now, I want to know if the distribution of this subset that I have created is similar to the distribution of the original, larger sample. </p>
<p>What ... | g64915 | [
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<p>I have a variance-covariance matrix, $\mathrm{V}$. This allows me to take a vector, $x$ of independent random variables drawn from a known distribution, and induce a required variance-covariance structure to give a correlated random variable $y$ from:</p>
<p>$y = \mathrm{V}^{\frac{1}{2}} x$</p>
<p>Because $\mathr... | g64916 | [
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<p>I need to analyse if there's a difference between poor and rich European countries (using a GDP per capita index variable) and look if it has an effect on the variable environment.</p>
<p>The GDP per capita variable is a ratio variable going from 44-..., while the environment variable is a nominal variable with two... | g23278 | [
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<p>I am analyzing data from different dichotomous variables. When analyzing association between these variables, what is the most recommended method?</p> | g49711 | [
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<p>If I am looking at sports data of a whole league over a year:</p>
<pre><code>Dependent Variable = Goals Scored
Independent Variables:
X1 = Traditional Home Uniforms
X2 = Retro Home Uniforms
X3 = Secondary Home Uniforms
Controls:
A whole bunch
</code></pre>
<p>My objective is to see what the effect of different ... | g64917 | [
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... |
<p>If I am looking at sports data of dozens of soccer leagues over a year:</p>
<pre><code>Dependent Variable = Goals Scored
Independent Variables:
X1 = Traditional Home Uniforms
X2 = Retro Home Uniforms
X3 = Secondary Home Uniforms
Controls:
A whole bunch
Most importantly--Every team has a rank (1-50) from the prev... | g45286 | [
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<p>I have been practicing some simple linear regression exercises lately and have been deeply challenged by the following question. While the part (A) is something I can concur, the proceeding parts baffled me in many ways.</p>
<p>In general, what I am challenged with is the (Value, Value) expressions.</p>
<p>Appreci... | g23280 | [
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<p>I am trying to run a factor analysis (SPSS) using principal axis factoring with an oblique (or promax) rotation because the variables are highly correlated. However, the output for "total variance explained" does not give any information on "extraction sum of squares" and "rotation sums" as it does if I use principa... | g64918 | [
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0.021121248602867126,
-0.04... |
<p>I was wondering, what is the meaning of operators in anova or regression formulas in R</p>
<p>For example</p>
<ul>
<li>"<strong>+</strong>" aov <- aov(x~time+sample, data=data) -> repeated mesures anova?</li>
<li>"<strong>*</strong>" aov <- aov(x~time*sample, data=data) -> two way anova?</li>
<li>"<strong>/<... | g43069 | [
-0.028185462579131126,
0.0013942174846306443,
-0.0292180385440588,
0.039672836661338806,
0.00691403029486537,
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0.0186870526522398,
0.0014650467783212662,
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0.019136007875204086,
-0.0728474035859108,
0.07162920385599136,
0.026826564222574234,
0.032... |
<p>The Wikipedia article of the log-normal distribution <a href="http://en.wikipedia.org/wiki/Log-normal_distribution" rel="nofollow">says</a> </p>
<blockquote>
<p>If $X$ is a random variable with a normal distribution, then $Y = \exp(X)$
has a log-normal distribution; likewise, if $Y$ is
log-normally distribute... | g583 | [
0.022127948701381683,
0.052102696150541306,
-0.004394620656967163,
0.0016368934884667397,
0.024347269907593727,
-0.033991824835538864,
0.05466683581471443,
-0.014938239939510822,
0.016872618347406387,
0.014774308539927006,
0.008754015900194645,
0.016442926600575447,
0.032225336879491806,
0... |
<p>My data consists of several continuous measurements and some dummy variables representing the years the measurements have been made.
Now, I want to learn a neural network with the data.
Therefore, I am zScore-normalizing all variables, including the dummy variables. However, I wonder if this is a reasonable approac... | g64919 | [
0.04405451938509941,
0.010208973661065102,
0.005684128031134605,
-0.019392753019928932,
-0.03153339773416519,
0.011050418950617313,
0.04031969606876373,
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-0.006927302107214928,
0.024619588628411293,
0.012059631757438183,
0.012987563386559486,
-... |
<p>What is the difference between linear regression and logistic regression?</p>
<p>When would you use each?</p> | g64920 | [
0.06851454079151154,
-0.04099978506565094,
0.009607542306184769,
0.0015137866139411926,
0.02888176031410694,
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-0.023826856166124344,
0.022494623437523842,
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-0.049027469009160995,
0.017639415338635445,
0.021774016320705414,
0.02429058402776718,
0.0... |
<p>Five months ago, jbowman posted a very useful answer to estimate the break point in a broken stick model with random effects in R. I never use "computing" like <code>ifelse</code> and I would like to estimate two break points. I should write two other functions like <code>b1</code> and <code>b2</code> but I don't kn... | g706 | [
-0.008733770810067654,
-0.07149181514978409,
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0.0059392936527729034,
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0.0386778898537159,
0.008414044044911861,
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-0.02406064048409462,
-0.05399303883314133,
0.028437834233045578,
-0.015161563642323017,
0.0... |
<p>I have a database with 500 records. I want to split these records to 75% and 25% *randomly*in order to use the different datasets for training and testing to machine learning algorithms. Does anyone knows how to do that? For example using an sql query</p> | g23283 | [
-0.000027733407478081062,
0.010143246501684189,
-0.016877155750989914,
-0.0704263299703598,
-0.040673691779375076,
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0.08765701204538345,
0.004982988350093365,
-0.003513166680932045,
0.02148461528122425,
0.006280929781496525,
0.017641078680753708,
... |
<p>Assume a linear mixing model $x = As$, where $x = (x_{0}, ..., x_{n})^T$ are linear mixtures of $s = (s_{0}, ..., s_{n})^T$, and $A$ is the mixing matrix.</p>
<p>Now, if I introduce additive noise to this system, that is,
$x = As + e$, where $e = (e_{0}, ..., e_{n})$, what are the relations between $e_{0}, ..., e_{... | g64921 | [
0.018845221027731895,
-0.03600846603512764,
-0.011308938264846802,
-0.04890146106481552,
0.03092840686440468,
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0.01658579520881176,
0.01720453053712845,
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-0.0728648379445076,
0.012101776897907257,
0.02113620564341545,
0.050134... |
<p>I have a markovian process with an initial state distribution $p(Z_0)$; i want to predict $Z_i$ for a fixed $i$ and i observe $Z_{i+j}$. However, the catch is that $j$ is also a hidden variable with a distribution $p(j)$. How can i effectively compute $p(Z_i| Z_{i+j} )$?</p>
<p>Some additional information about the... | g23287 | [
0.027849560603499413,
-0.02863684855401516,
-0.020555702969431877,
-0.026541801169514656,
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0.05623134225606918,
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-0.0381634384393692,
-0.06379330158233643,
0.05101925879716873,
0.055251870304346085,
0.01... |
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