question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I ran a data set containing ages through SAS npar1way first, but a reviewer wanted standard errors, so that motivated a smooth bootstrap. Since I could not use survyselect, I had to code a data step. I think it's set up correctly. I ran 10,000, 20,000 and 100,000 replicates. I need some feedback on my findings. ... | 36,275 |
<p>Currently I am skimming through a couple of papers in well established journals!
I became curious when I found papers with linear regression models using the Herfindahl index as the dependent variable. I thought such a continuous but limited variable had to be used in combination with the ln!</p>
<p>Could any of y... | 36,276 |
<p>I am slightly getting confused at the presentation of regression models.</p>
<p>What would be the difference between these two:</p>
<p>$y = \beta_0 + \beta_1 x_1 + \beta_2 x_2$</p>
<p>$y = \gamma_0 + \gamma_1 x_1 + \gamma_2 x_2$</p>
<p>When are the different notations to be used?</p>
<p>I'm unable to search thi... | 73,790 |
<p>How would one go about testing an implementation of a Bayes Factor calculation? The analogue in Frequentist hypothesis testing is fairly straightforward: generate data according to the null hypothesis, use the code to generate a p-value, repeat thousands of times with different random seeds, and look for uniformity ... | 73,791 |
<p>I have data that includes the number of students in a class and the percentage of that group who achieved a preset pass level in a standard test. I have this data for a number if different schools in two population samples, about 30 schools in each. The class sizes differ considerably, so it seems take sense to use ... | 36,278 |
<p>I am modelling eyetracking data where people can look at one of two objects on the screen. Our experimental manipulation is meant to increase the likelihood that they look at object A over object B. However, the effect isn't likely to be linear and what we actually hypothesize is that our control participants will... | 47,846 |
<p>I would like to regress the influence of income, education, marital status etc. on life satisfaction. The data I use is from the SHARE survey β life satisfaction can take values of 1β10, most values are around 6β8.</p>
<p>OLS regression seems to be a poor choice to me, as it might produce predicted values outside t... | 36,279 |
<p>I have two time-series:</p>
<ol>
<li>A proxy for the market risk premium (ERP; red line)</li>
<li>The risk-free rate, proxied by a government bond (blue line)</li>
</ol>
<p><img src="http://i.stack.imgur.com/evTDC.png" alt="Risk premium proxy and risk-free rate over time"></p>
<p>I want to test if the risk-free r... | 47,851 |
<p>I did a one-way ANOVA followed by a Tukey's test to compare the means of different treatments.</p>
<p>Let's say the treatments are A, B and C.</p>
<p>The table of multiple comparisons tells me there is a significant difference between B and C.
However, these two are not significantly different from A, and therefor... | 3,017 |
<p>I'm trying to use the ridge.cv() function in R. The <a href="http://www.inside-r.org/packages/cran/parcor/docs/ridge.cv" rel="nofollow">documentation</a> says that the input y is the "vector of responses".</p>
<p>What exactly does that mean?</p> | 36,284 |
<p>What do I need to measure interaction between variables in a particular equation?</p>
<p>For e.g.
Me just taking 50 grams of protein everyday will help me health wise.
Me just doing exercise for 1 hour everyday will help me health wise.
Me just stretching 1 hour everyday will help me health wise.
Etc.</p>
<p>But ... | 73,792 |
<p>I sometimes have the situation where I have from several dozen to over 100 linear models to perform hypothesis tests on. They have the same predictor variables, but different response variables. </p>
<p>Let's say I have 100 models and each model has four p-values-- one for the intercept, one each for two main effec... | 30,600 |
<p>Suppose $U_{(1)} , \dots , U_{(n)}$ is order statistics a random sample from $U(0,1)$.how can find joint Probability density function limit distribution of statistics $T_n=(nU_{(1)},nU_{(2)}).$</p> | 36,288 |
<p>My question is exactly the title : to whom can we report a problem with SAS ?</p>
<p>Below is an example. This problem is not really severe but somewhat dangerous (in fact I have just updated my example below after Aniko's comment; there was a confusion in the first version of this post). </p>
<p>Consider such a d... | 73,793 |
<p>I have a dataframe called "cleaned", which consists of about 300,000 rows and 13 variables. Except the dependent variable, all variables are categorical and have multiple levels ($\geq2$). The dependent variable is numeric and takes values ranging from -1,500 to 3,296, mostly positive. Here is a summary of the dataf... | 36,289 |
<p>Am trying to develop a predictive model using high-dimensional clinical data including laboratory values. The data space is sparse with 5k samples and 200 variables. The idea is to rank the variables using a feature selection method (IG, RF etc) and use top-ranking features for developing a predictive model. </p>
<... | 33,717 |
<p>I do a GLM containing 8 predictors on a multivariate data set. Six of these predictors encode effects that have actually been manipulated in my experiment (effects of interest), the other two predictors are noise-predictors of physiological side-effects that influence the data, but are not meant to. </p>
<p>It turn... | 73,794 |
<p>I am conducting analysis on 'Multi-Attribute Decision Making (MADM)', where I have two attributes (a1, a2) to characterize the quality of m alternative approaches. The first attribute, a1, is measured in percentage (hence does not have a unit), whereas the other has a unit. There are some alternatives that have zero... | 73,795 |
<p>We have a iid sequence of random variables $X_1, X_2, \dots, X_n$, where $E(X_i) = \mu$ and $var(X_i) = \sigma^2$. The sample mean $\bar{X}$ converges to $\mu$ at rate $\sqrt{n}$ thanks to the LLN. </p>
<p>If we have a continuous function $f()$, the continuous mapping theorem assures that $f(\bar X)$ converges to $... | 73,796 |
<p>I'm a complete newbie :)</p>
<p>I'm doing a study with a sample size of 10,000 from a population of about 745,000. Each sample represents a "percentage similarity". The great majority of the samples are around 97%-98% but a few are between 60% and 90%, that is, the distribution is heavily negatively skewed. Around ... | 36,297 |
<p>Let $ Z=X_1^2+X_2^2\cdots\cdots X_j^2 $, such that $X_i \sim \mathcal{N}(\mu_i,\sigma_i^2)$. All $X_i$'s are independent of each other and $\mu_i$ and $\sigma_i^2$ are all different from one another.</p>
<p>Question is:</p>
<p>1) What is the distribution of Z ?</p>
<p>2) If it is non-central Chi square distributi... | 49,816 |
<p>I have 2 correlation matrices $A$ and $B$ (using the Pearson's linear correlation coefficient through Matlab's <a href="http://www.mathworks.com/help/matlab/ref/corrcoef.html" rel="nofollow">corrcoef()</a>). I would like to quantify how much "more correlation" $A$ contains compared to $B$. Is there any standard metr... | 73,797 |
<p>I am working with a dataset where I need to use non-parametric stats (won't go into details). It is behavioral data on captive animals ($n=8$), where $4$ treatments were introduced $3$ different times randomly. I have tested for difference in my repeats using a Friedman test. None were found. I am looking for a way ... | 73,798 |
<p>I have quarterly unbalanced Panel data and I want to de-trend my dependent variable to make it stationary. how do i do it? I don't want to take differences as it will shorten my observations. The residual series that I get after regressing my dependent variable on time trend does not remove unit root for data . It s... | 73,799 |
<p>Can someone please provide examples of labelled and unlabelled data? I have been reading definitions of semi supervised learning but it does not make clear on what the two actually are.</p> | 73,800 |
<p>I'm trying to build a monte-carlo simulation that can revise it's distribution of outcomes of a project based on observed measurements after the project has started.</p>
<p><strong>I have a few questions about the best way to do this. I'm not a statistician, so please correct me if I am doing something wildly wrong... | 494 |
<p>I've seen in <a href="http://www.khanacademy.org/video?v=hxZ6uooEJOk" rel="nofollow">video</a> lessons that if the sample size is big enough (n>30) sample distribution standard deviation can be approximated by sample standard deviation. How do we get the sample distribution standard deviation if sample size is small... | 73,801 |
<p>Related to <a href="http://stats.stackexchange.com/questions/50537/should-one-remove-highly-correlated-variables-before-doing-pca">Should one remove highly correlated variables before doing PCA?</a>, PCA is used a lot in population genetics to essentially cluster individuals into ethnic group based on their genetic ... | 36,301 |
<p>I was wondering whether the following mechanical selection procedure will result in a possible bias. First let me introduce the first procedure, we start with a model and only look at the t-value and possibly correct them for it (heteroskedasticity / autocorrelation). We then only add variables into our final model ... | 36,302 |
<p>I am working on a prediction model in which I have several factor variables that have many levels. These factor variables have a nested structure, in the form of a Category, a Sub-Category, and a Sub-Sub-Category. For example suppose that I had one field that was the type of device a user browsed the website with (p... | 73,802 |
<p>I want to know if the initiation of a state Renewable Portfolio Standard affects the level of renewable energy output in that state.</p>
<p>I don't have access to Stata right now, so I'm stuck using excel. I have data for renewable energy output for all thirty states that have initiated Renewable Portfolio Standar... | 36,303 |
<p>I am working with culture cells where one dish has been transfected with a scrambled knockdown clone and two dishes which have been transfected with two knockdown clones each knocking down the expression of a single gene. </p>
<p>An example of an experiment I have performed is to measure the mitochondrial membrane ... | 73,803 |
<p>Can you please tell me the formula (I am more interested in the approach than the answer) to answer the following question?
Letβs say I drive an unreliable car that is not expected to start 1 out of every 5 mornings. When the car doesn't start, I miss work. I work 5 days a week.<br>
What is the expected number of d... | 36,304 |
<p>For fantasy basketball, I want to quantify a player's output based on his Points, Rebounds, Assists, Steals, 3s, and Blocks production.</p>
<p>Let's pretend that over the course of an imaginary basketball season there are total of 245,000 Points, 100,000 Rebounds, 53,000 Assists, 18,000 steals, 12,000 blocks, and 1... | 73,804 |
<p>I am trying to manually calculate P-Value (right tailed) from F-Test to understand it better. Would like to learn how the value obtained from the F-Test.</p>
<p>Have obtained the below parameters,</p>
<pre><code>ndf = 1
ddf = 238
Ξ(ndf/2,ddf/2) = 0.162651
critical value, x (Ξ±=0.005) = 8.028403472
F_stat = 8983.641... | 73,805 |
<p>I have a group of 200 children who came to clinic at months 0, 1, 2, 3, 6, 9, and 12 this year. At each clinic visit the children were weighed.</p>
<pre><code># Set seed to create reproducible example data
set.seed(50)
# Create patient ID numbers, genders, and ages
control <- NULL
control$Age_0 = round(runif(20... | 73,806 |
<p>I have been trying to implement a Bayesian inference procedure from scratch for a specific problem, but I have implemented the procedure, and it doesn't seem to work. </p>
<p>Since, I can't just post the code online and ask community to debug my code, I was wondering if someone could provide with a broader checklis... | 73,807 |
<p>I have some $d$-dimensional data points ($d \ge 2$). I want map them to a circle such that locality is preserved as much as possible. </p>
<p>I know that PCA only maps points to a line ($d'=1$) or a plane ($d'=2$), but I want them on a circle. </p> | 36,306 |
<p>I'm wondering how to fit multivariate linear mixed model and finding multivariate BLUP in R. I'd appreciate if someone come up with example and R code. Thanks</p>
<p><strong>Edit</strong></p>
<p>I wonder how to fit multivariate linear mixed model with <code>lme4</code>. I fitted univariate linear mixed models with... | 16,787 |
<p>Modularity: I understand that modularity is supposed to represent sophistication of structure on a macro level, but what does it mean on the individual level? </p>
<p>Page Rank: I'm dealing with a dataset of people asking questions and answering questions. If someone answers a question, the arrow is drawn from the ... | 73,808 |
<p>I am a complete newbie in statistical modeling and I never got the opportunity to learn how to express a model in algebraic form and its respective matrix notation. I know how to define models in R code, but I do not understand how to write it in mathematic form, e.g. with Ξ² as the vector of a fixed effect. I am try... | 73,809 |
<p>According to <a href="http://jarrodwilcox.com/expert-investor/diversification-helps-growth/" rel="nofollow">this extract of a paper</a> posted on the web, the average return of a fair coin flip that pays 100% for heads and loses 50 percent for tails over 3 periods is 25 percent per period, while the geometric mean o... | 73,810 |
<p>Assume there are two candidate models, $\hat{f}(\beta)$ and $\hat{g}(\beta,\theta)$. If the true data generating process is $f(\beta)$, then $\hat{g}(\beta,\theta)$ is unbiased but inefficient. If, on the other hand, the true DGP is $g(\beta, \theta)$, then $\hat{f}(\beta)$ is biased.</p>
<p>Under a classical model... | 73,811 |
<p>DISCLAIMER: I don't have a lot of stats experience, so please don't laugh too hard if my question is trivial.</p>
<p>I have run an experiment with 5 categorical factors. The factors have anywhere between 2 and 8 levels each. I have one response variable, which is continuous in the range of 0 to 100. All-in-all, I h... | 73,812 |
<p>I use a MLP with one hidden layer (15 nodes) and one output node. I use a sigmoid activation function, atan as error function, the error itself is calculated with MSE, 5-fold crossvalidation, resilient backpropagation for a batched binary classification task where within each batch approx. 1000 samples are available... | 47,877 |
<p>I am using SPSS to analyse the 3-way mixed model ANOVA of my study.
I have split my variables down to interpret simple interaction effects and found that whilst the graph displays an interaction effect between the variables, the spss output (test within subjects and test between subjects) does not display any signif... | 73,813 |
<p>Ryan Tibshirani introduced once a more general type of Lasso, where the regularizer is
$$\parallel D \alpha \parallel_1$$
instead of $\parallel \alpha \parallel_1$.
<a href="http://www.stat.cmu.edu/~ryantibs/papers/genlasso.pdf" rel="nofollow">See paper</a></p>
<p>However, there is nearly no discussion about this f... | 73,814 |
<p>Someone has surveyed a number of people and put the results in a database (Survey 1). Each observation has additional information that, for any subpopulation (men only, young only, etc.), gives a national-level estimate of the number of people in that subpopulation, as well as a confidence interval for that estimate... | 36,312 |
<p>Gelman & Hill (2006) say:</p>
<blockquote>
<p>In Bugs, missing outcomes in a regression can be handled easily by
simply including the data vector, NAβs and all. Bugs explicitly
models the outcome variable, and so it is trivial to use this model
to, in eο¬ect, impute missing values at each iteration.</p>
... | 30,695 |
<p>I want to compare the distance/similarity of 2D flood frequency data maps. The maps are square with YxY grid size and in each cell of the map is stored its flood frequency. For example in a 5x5 grid we may have this two flood frequency maps of the same area for the past 10 years, where we observe how many times the ... | 36,315 |
<p>In gaussian_kde from scipy library there are two methods to estimate the bandwidth, "scott" and "silverman"</p>
<p>The silverman rule of thumb is explained <a href="http://en.wikipedia.org/wiki/Kernel_density_estimation#Practical_estimation_of_the_bandwidth" rel="nofollow">here</a> and the equivalent function in R ... | 73,815 |
<p>Let $$X_1,\dots,X_m$$ are i.i.d. with distribution function $F$ and $$Y_1,\dots,Y_n$$ are i.i.d. with distribution function $G$. Suppose that there exists an unknown function $\psi:\mathbb{R}\mapsto\mathbb{R}$ such that $\psi(X_i)\sim N(0,1)$ and $\psi(Y_j)\sim N(0,\sigma^2)$ for all $i=1,\dots,m$ and $j=1,\dots,n$.... | 73,816 |
<p>I'm not used to using variables in the date format in R. I'm just wondering if it is possible to add a date variable as an explanatory variable in a linear regression model. If it's possible, how can we interpret the coefficient? Is it the effect of one day on the outcome variable? </p>
<p>See my <a href="https://g... | 73,817 |
<p>I want to run Levene's test to test the equality of variances between a full sample a number of sub-samples. I can't find anything about Levene's test that states whether this would violate the assumptions of the test. In other words, given the null hypothesis that $\mathrm{Var}(X_{1}) = \mathrm{Var}(X_{2})$, does L... | 73,818 |
<p>Is there a way to simplify this equation? </p>
<p>$$\dbinom{8}{1} + \dbinom{8}{2} + \dbinom{8}{3} + \dbinom{8}{4} + \dbinom{8}{5} + \dbinom{8}{6} + \dbinom{8}{7} + \dbinom{8}{8}$$</p>
<p>Or more generally,</p>
<p>$$\sum_{k=1}^{n}\dbinom{n}{k}$$</p> | 25,114 |
<p>Say I have below example data, where rows are observations and columns are variables, and NAs stand for missing values.</p>
<pre><code> 1 2 NA 4 5 6 14 5 2
6 13 7 1 11 4 NA 9 6
15 12 3 12 NA 8 3 7 12
8 1 NA 7 8 9 4 6 1
</code></pre>
<p>I want to impute the missing values by regression (I know I can... | 73,819 |
<p>I have two dependent groups that could have a disease before and after a treatment.
My sample size is 12214 subjects.
Before the treatment, 7 of them had the disease and after the treatment 14 of them had the disease.</p>
<p>Percentages of total sample are very low although the number of patients with disease doubl... | 73,820 |
<p>I paper I am trying to replicate used Eviews to estimate their state space model (by maximizing the associated maximum likelihood). They used the BHHH and Marquardt algorithms.</p>
<p>My question is given that the Marquardt algorithm is generally used to solve least square type problems what is Eviews doing to allo... | 36,322 |
<p>I'm really new to stats and R and I suspect I'm missing something obvious. I have a set of memberships all who start after a point in time (six months ago). I have done my query to estimate the number of days in the membership to today marking those still ongoing as censored. I've done my plot from the data so the ... | 73,821 |
<p>I often hear the claim that Bayesian statistics can be highly subjective. The main argument being that inference depends on the choice of a prior (even though one could use the principle of indifference o maximum entropy to choose a prior). In comparison, the claim goes, frequentist statistics is in general more obj... | 73,822 |
<p>How to guess what should be the starting values for beta estimates, which we need to specify in PARMS or PARAMETERS statement while using PROC NLIN (PROC NLIN is used to run non-linear regression in SAS)</p> | 30,769 |
<p>How can I test heteroskedasticity of a time series in R? I have heard of two tests <code>McLeod.Li.test</code> and <code>bptest</code> (Breusch-Pagan test). Can I use these two tests? and what are the differences and assumptions of these tests if I can use them?</p>
<p>Thanks</p> | 73,823 |
<p>How do I interpret this model:</p>
<p>$$
Price = -7.095 - 9.471[\ln(Number Of Different Kinds Of Fruits)] + 53.942 \sqrt{Number Of Customer} + ...
$$</p>
<p>Is that:</p>
<ul>
<li>If there are no kinds of fruits nor visitors nor other variables, the expected average price will be -7.095</li>
<li>If the natural log... | 73,824 |
<p>I am investigating a common discrepancy between male and female self-reports on a survey about sexual experiences. Generally, women report ~2/3 higher rates then men do. I have modified the survey and now need to find out if/how the discrepancy between males' and females' reporting rates may have changed. Males a... | 73,825 |
<p>I am trying to find a more aesthetic way to present an interaction with a quadratic term in a logistic regression (categorisation of continuous variable is not appropriate).</p>
<p>For a simpler example I use a linear term.</p>
<pre><code>set.seed(1)
df<-data.frame(y=factor(rbinom(50,1,0.5)),var1=rnorm(50),var... | 73,826 |
<p>I overhead a professor speak about the Cauchy meta-distribution, but I am unable to find anything about it on the web. My question is what is the Cauchy meta distribution and what is the theory behind it?</p> | 73,827 |
<p>I'm trying to find the probability that two randomly-selected letters from "average" text in a language will be the same. </p>
<p>For example, if my hypothetical language contains four letters which each occur on average with the following frequency:</p>
<pre><code>A = 60%
B = 25%
C = 10%
D = 5%
</code></pre>
<p... | 73,828 |
<p>Please see the model below (<a href="http://i.stack.imgur.com/CspnD.png" rel="nofollow">link to bigger image</a>). The independent variables are properties of 2500 companies from 32 countries, trying to explain companies' CSR (corporate social responsibility) score. </p>
<p>I am worried about the VIF scores of espe... | 36,327 |
<p>I want to see if there is a correlation (or any sort of relationship) between two time series I am working with.</p>
<p>One of them is a times series of temperature data, the other one is concentration of a substance. I am trying to see if there is a relationship between the concentration and temperature.</p>
<p>H... | 73,829 |
<p>Lets say I want to generate data with particular <strong>association matrix</strong>. I am taking <a href="http://en.wikipedia.org/wiki/Phi_coefficient" rel="nofollow">phi coefficient</a>` as measure degree of association.</p>
<p>Here are examples using R. </p>
<pre><code> require(psych)
var1 <- sample(c... | 73,830 |
<p>I have a fairly basic statistics application question. Lets say I have a set of four fold-change values, representing the abundance of a factor as it passes through four consecutive time points:</p>
<pre><code>x<-c(1.0, 1.2, 15.3, 0.2)
</code></pre>
<p>And I want to define its "trend" ie, a single-number repres... | 36,329 |
<p>Suppose I have two events $B$ and $A^c$ and I wish to compute the probability of their intersection. I just want to ensure that the following proof holds (i.e., is correct -- I'm a little rusty). <strong>Updated!</strong> Assume the events are independent.</p>
<p>\begin{gather*}
P(A^c) = 1- P(A) \\
\end{gather*}... | 36,332 |
<p>I am trying to carry out the discretized process suggested by the authors in this <a href="http://web.mit.edu/dbertsim/www/papers/Finance/Optimal%20control%20of%20execution%20costs.pdf" rel="nofollow">paper</a>, i.e. the numerical optimization, and would be grateful for some pseudo code or better still R code that m... | 73,831 |
<p>I followed <a href="http://rtutorialseries.blogspot.hk/2010/01/r-tutorial-series-basic-hierarchical.html" rel="nofollow">this tutorial</a> to learn Hierarchical Linear Regression (HLR) in R, but couldn't understand how to interpret its sample output of <code>>anova(model1,model2,model3)</code></p>
<p><img src="h... | 36,333 |
<p>The following figures show examples of ROC curves:</p>
<p><img src="http://i.stack.imgur.com/yPqte.png" alt="t1"></p>
<p>First of all ignoring the picture, from a logical point one can say:
When the <strong>cutoff</strong> value <strong>decreases</strong>, more and more cases are allocated to class 1 and therefore... | 73,832 |
<p>I have a series of daily log returns and I am looking to fit them to an AR() process. </p>
<p>Any suggestions?</p> | 37,761 |
<p>After R reads the data, say-</p>
<pre><code>v1 <- c(1,1,1,1,1,1,1,1,1,1,3,3,3,3,3,4,5,6)
v2 <- c(1,2,1,1,1,1,2,1,2,1,3,4,3,3,3,4,6,5)
v3 <- c(3,3,3,3,3,1,1,1,1,1,1,1,1,1,1,5,4,6)
v4 <- c(3,3,4,3,3,1,1,2,1,1,1,1,2,1,1,5,6,4)
v5 <- c(1,1,1,1,1,3,3,3,3,3,1,1,1,1,1,6,4,5)
v6 <- c(1,1,1,2,1,3,3,3,4,3,1... | 73,833 |
<p>I have a training set with 4 different 3D position vectors as some of the features. I have defined a new 3D coordinate system based on the first 3 of these position vectors to achieve translational and rotational invariance. Then transformed the original points to this new system. Since the last point also originall... | 43,892 |
<p>I am trying to come up with estimates on the outcomes from a layered-earth inversion calculation whereby the calculation provides a posterior covariance matrix for the best-fitting model parameters given the data. In particular, I want to see how long a particular feature of the model persists from the surface (ie,... | 73,834 |
<p>Say I have a set of classifier models, each generated using feature selection inside a repeated k-fold cross-validation. Each classifier model is generated using a different set of regularization parameters or hyperparameters. </p>
<p>I understand that choosing the 'best' model of this set, i.e. one that yields bes... | 36,336 |
<p>CLT states in short, that sum/mean of random iid variables from almost any distribution approaches normal distribution. </p>
<p>I failed to find information about asymptotic behavior of sample variance when sample is drawn from unknown distribution. Do we have any reason to believe, that variance of random iid vari... | 36,337 |
<p>The <a href="http://en.wikipedia.org/wiki/Finite_difference#Forward.2C_backward.2C_and_central_differences" rel="nofollow">central difference</a> is a method to approximate numerically the derivative of a function sampled at discrete intervals. In R, one would do:</p>
<pre><code>n<-100
y<-cumsum(rnorm(n))
y_p... | 73,835 |
<p>suppose we have a stream of sentences and we need to compare each new sentence with previously received ones . For example , with sentences received in last 30 minutes. What is the best method to do that ? can we use Mahalanobis distance for this ? How ?</p> | 38,146 |
<h2>Scenario:</h2>
<p>Consider a statement, e.g. "This movie is an action"
Then let people vote on that. 1-5 where 1 is "Not action", 3 is "Some action" and 5 is "Pure action". </p>
<h2>Question</h2>
<p>How does one determine how accurate the the statement from the voting result?</p>
<p>1000 votes where 900 is a 5 ... | 36,340 |
<p>I have some satellite tag time-at-depth (TAD) frequency data that I would like some help with.</p>
<p>The data was transmitted via satellite as percent time spent in each of 7 depth bins (0m, 0-1m, 1-10m, 10-50m etc.), binned over 6-hour intervals. I categorized each row of data corresponding to a date and time in... | 36,345 |
<p>Since the mean of the residuals should be close to zero and with my calculations yield the following result:</p>
<pre><code>> mean(resid(trees.lm)
[1] -3.065293e-17
</code></pre>
<p>is it correct to stipulate that the mean is close to zero?</p>
<p>My second question is as follows: While I am working with the g... | 36,346 |
<p>I am reading an article that explores correlation between two variables, X and Y. Usually, if the scatter plot show something like this, we can claim that there is a strong correlation of X and Y.</p>
<pre><code>Y
|
| o
| o o
| o
| o o
| o
| o
| o
+--------------... | 73,836 |
<p>I'm having a problem using the group function in TraMineR. I have a data set that contains SPELL data, so multiple rows per case. I also have demographic data per case, at one row per case. I merge these together and end up with data that has a demographic covariate per row, so multiple rows per case. An example of ... | 73,837 |
<p>I am trying to estimate a binomial proportion p, say, from a sample of binomials. There are k subjects. Associated with each subject is a sample size $n_i$ and a count $x_i$ of items, where $x_i$ is distributed as a binomial $(p, n_i)$. I can assume that the sample sizes are not a function of $p$. </p>
<p>In sampli... | 41,434 |
<p>I am dealing with a text classification problem. Where I need to assign tags to a document. The amount of tags I need to assign varies from 1 to 5. I am struggling somewhat on how I should tackle this problem. What I tried was to encode every combination of tags with LabelEncoder() from scikit-learn, I framed it as ... | 73,838 |
<p>I have some measurement results (about 10000 or even more). How can I say (which methods should I use and how to apply them) to check if my data is time series or is a statistical sample?</p> | 49,924 |
<p>I am trying to do a small case study in 24 hours + change.</p>
<p>For a dataset, I'm using <a href="http://ghtorrent.org" rel="nofollow">GHTorrent.org</a>.</p>
<p>A general assumption about virtual work is that richer media leads to greater productivity. I have decided to focus on <a href="http://github.com" rel="... | 73,839 |
<p>I have a observation sequence of around 1000 samples, each observation is a 10 dim vector. I am trying to learn an HMM model based on this. Specifically I am using the GaussianHMM based on this example: <a href="http://scikit-learn.org/stable/auto_examples/applications/plot_hmm_stock_analysis.html#example-applicatio... | 73,840 |
<p>What Exactly is the difference between decode and score? The documentation seems pretty sparse regarding this.</p>
<p>My guess is that:
decode represents the probability of the best sequence of states for a observation sequence.
score represents the sum of probabilities of all state sequences for a observation sequ... | 73,841 |
<p>I used Radial basis function and pseudo inverse to train neurons and then test it. Everything works here. But I read I can use gradient descent method instead of using pseudo inverse which sometimes may be hard to do (may run out of memory, may take too long to compute).
But I don't understand few things here.</p>
... | 36,350 |
<p>I have trouble interpreting interaction plots when there is an interaction between the two independent variables.</p>
<p>The following graphs are from <a href="http://courses.washington.edu/smartpsy/interactions.htm">this</a> site:</p>
<p>Here, $A$ and $B$ are the independent variables and $DV$ is the dependent va... | 36,351 |
<p>I don't know how to grasp what this question is asking, nor how to attempt to solve it...</p>
<p>The Polk Company reported that the average age of a car on US roads in a recent year was 7.5 years. Suppose the distribution of ages of cars on US roads is approximately bell-shaped. If 95% of the ages are between 1 yea... | 36,352 |
<p>If $X_i$ is exponentially distributed $(i=1,...,n)$ with parameter $\lambda$ and $X_i$'s are mutually independent, what is the expectation of</p>
<p>$$ \left(\sum_{i=1}^n {X_i} \right)^2$$</p>
<p>in terms of $n$ and $\lambda$ and possibly other constants?</p>
<p><strong>Note:</strong> This question has gotten a m... | 36,354 |
<p>I am trying to compute the standard error of the sample <a href="http://en.wikipedia.org/wiki/Spectral_risk_measure" rel="nofollow">spectral risk measure</a>, which is used as a metric for portfolio risk. Briefly, a sample spectral risk measure is defined as
$q = \sum_i w_i x_{(i)}$, where $x_{(i)}$ are the sample ... | 36,355 |
<p>The <a href="http://en.wikipedia.org/wiki/Kernel_trick">kernel trick</a> is used in several machine learning models (e.g. <a href="http://en.wikipedia.org/wiki/Support_vector_machine">SVM</a>). It was first introduced in the "Theoretical foundations of the potential function method in pattern recognition learning" ... | 660 |
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