question stringlengths 37 38.8k | group_id int64 0 74.5k |
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<p>[I asked this on StackOverflow and was told it would be a better fit here]</p>
<p>I am including a basic recommendation engine in a very small project for my final exam. I understand the code and the math but I am not too certain as to when I should update the values. </p>
<p>In this project it would be fairly sim... | 71,016 |
<p>The <code>lme4</code> package in R includes the <code>cake</code> dataset. </p>
<pre><code>library(lme4)
head(cake[,2:4], 20)
recipe temperature angle
1 A 175 42
2 A 185 46
3 A 195 47
4 A 205 39
5 A 215 53
6 A 225 ... | 71,017 |
<p>The chloride concentration at depth $x$ mm at time $t$ is:
$$
\text{C}(x,t)=\text{Cs}(1-\text{erf}(x/(2(D*t)^{0.5}))
$$
where $\text{Cs}$ is chloride surface concentration with Lognormal distribution, $D$ is the diffusion coefficient with normal distribution, and $\text{erf}$ is error function. On the other hand, w... | 71,018 |
<p>In several different contexts we invoke the <a href="http://en.wikipedia.org/wiki/Central_limit_theorem">central limit theorem</a> to justify whatever statistical method we want to adopt (e.g., approximate the binomial distribution by a normal distribution). I understand the technical details as to why the theorem i... | 49,387 |
<p>I get this question frequently enough in my statistics consulting work, that I thought I'd post it here. I have an answer, which is posted below, but I was keen to hear what others have to say.</p>
<p><strong>Question:</strong> If you have two variables that are not normally distributed, should you use Spearman's
r... | 71,019 |
<p>I'm looking for an <code>R</code> package for estimating the coefficients of logit models with individual fixed-effect (individual intercept) using Chamberlain's 1980 estimator. It is often known as Chamberlain's fixed-effect logit estimator. </p>
<p>It's a classic estimator when dealing with binary outcome panel ... | 71,020 |
<p>Using Pearson's Correlation Coefficient, I have several variables that are highly correlated ($\rho = 0.978$ and $\rho = 0.989$ for 2 pairs of variables that are in my model).</p>
<p>The <em>reason</em> some of the variables are highly correlated is because one variable is used in the <em>calculation</em> for anoth... | 71,021 |
<p>Consider the following exponential expansion form:</p>
<p>$$ \exp\left[\sum_{k=1}^\infty \gamma_k x^k\right] = \sum_{j=0}^\infty\delta_j x^j $$
where $\gamma_k$'s are known, and $\delta_0=1$,
$$\delta_{j+1} = \frac{1}{j+1}\sum_{i=1}^{j+1}i\gamma_i\delta_{j+1-i}$$</p>
<p>Does anyone know how to prove it?</p> | 71,022 |
<p>for eg. if I have a class variable credit scoring with two classes good and bad, where #(good) = 700 and #(bad)= 300. I do not want to shorten my data. which technique I should use? I was using SVM but it is giving all bad as good in predictions.</p> | 32,303 |
<p>In the simulated Alternative Vote below, I had 10,000 people vote for 100 candidates using AV style voting (also known as instant runoff voting).</p>
<p>Most people want person #57 or person #78 to win, but neither was able to reach a majority.</p>
<ul>
<li>What math/stats function will allow me to eliminate those... | 71,023 |
<p>I came across a kind of classification problem.</p>
<p>Suppose I have a dataset with labels, where each label is one of a1, a2, a3, b1, and b2. I want to make a classifier that estimates "coarse" label, a or b.</p>
<p>Here is a concrete example. Imagine a set of animal images labeled by the its species. We want ma... | 32,305 |
<p>I am trying to analyse my biological data which is derived from flow cytometry and describes the percentage of cells with a certain property. Data is available for two conditions: once the cells areuntreated and once the cells were stimulated. For the untreated condition I analysed 57 samples, for the stimulated con... | 71,024 |
<p>What is the most suitable optimization algorithm for optimizing maximum likelihood estimator? In excel I used GRG non linear optimization algorithm, is that good enough?</p>
<p>I want to write my own code to understand optimization better so I want to choose most suitable non linear constrained optimization algo fo... | 32,306 |
<p>For finding the Alias of main effect <em>A</em> , i started as the following :</p>
<p>$\text{A}$$\times$ $\text{A}{B}^3$$=\text{A}^2\text{B}^3={(\text{A}^2\text{B}^3})^2=\text{A}^4\text{B}^6=\text{B}^2$(mod $4$)$={(\text{B}^2)}^2=\text{B}^4=0$(mod $4$)</p>
<p>Where am i doing mistake?</p> | 71,025 |
<p>After fitting a multinomial model to my data with the "multinom" function (package nnet), I want to show the effect of selected variables controlling for other variable values. I know that the "effects" package do mainly what I want, but I want to be able to calculate the prediction error (confidence interval) by my... | 71,026 |
<p>I have a simulated distribution with mean 12.53% and standard deviation 11.83%. The sample size is big enough (10,000) to assume it is a Normal distribution. </p>
<p>How do I properly test if the value "26.05%" is significantly larger than the mean 12.53%?
Can anyone please help me to write the null hypothesis, as... | 71,027 |
<p>From my understanding of the genetic algorithm the population consists of individuals, where each individual is a potential solution made up of "genes", and each gene is a variable. So for a cost function that takes in 3 variables the individuals will have 3 genes.</p>
<p>The optimization happens by selection (pick... | 71,028 |
<p>Input matrix M x N, M rows (number of samples), N cols (dimesionality of data).</p>
<p>But I don't understand why we must transpose matrix when put it in np.cov? </p>
<pre><code>def pca():
#M x N
xs= np.loadtxt("data_3d.txt",delimiter=" ", skiprows=1, usecols=(0,1,2))
print xs.shape
# print xs
... | 32,307 |
<p>I have an exercise given to me during the recruitment process which asks to calculate the next year's January hourly forward prices for an asset given the historical hourly prices of that asset and next year's January average price (average of all hours in that period).
The exercise asks to take account of the seas... | 32,308 |
<p>I use a memory-based learning model to predict human scores in a [0, 10] range (quiz results). As a forecast error metric I use Mean Absolute Error. I was wondering what is the relation between MAE and data distribution. How can i use the data (or the error) distribution to explain the error and possibly argue wheth... | 71,029 |
<p>Assume that there are 15 subjects and that a quantitative feature is measured for all subjects at three equally-spaced times points. The research of interest is to find out wether there is a linear trend across time. Admittedly the number of time points is quite limited, but what are the options for trend analysis? ... | 43,005 |
<p>I am trying to assess the goodness-of-fit or accuracy of 6 generalised linear models. I first assessed this using AUC (calculated from function auc1 described <a href="http://stats.stackexchange.com/questions/80399/can-someone-sort-me-out-regarding-the-calculation-of-auc">here</a>), and got results ranging from 0.65... | 71,030 |
<p>I read somewhere that Variational Bayes method is a generalization of the EM algorithm. Indeed, the iterative parts of the algorithms are very similar. In order to test whether the EM algorithm is a special version of the Variational Bayes, I tried the following:</p>
<ol>
<li><p>$Y$ is data, $X$ is the collection o... | 71,031 |
<p>How are PCA and classical MDS different? How about MDS versus nonmetric-MDS? Is there a time when you would prefer one over the other? How do the interpretations differ?</p> | 49,327 |
<p>I've read some of the answers here (specifically the 'Inter-rater reliability for ordinal or interval data' one). I'm still somewhat perplexed though!</p>
<p>I have data for 4 raters, who each rated every subject's CT scan, on two occasions, for the presence or absence of 9 signs. The two readings were separated by... | 32,313 |
<p>I'm trying to understand how exactly factors work in R. Let's say I want to run a regression using some sample data in R:</p>
<pre><code>> data(CO2)
> colnames(CO2)
[1] "Plant" "Type" "Treatment" "conc" "uptake"
> levels(CO2$Type)
[1] "Quebec" "Mississippi"
> levels(CO2$Treatment)
... | 71,032 |
<p>I took a probability course in university a few years ago, but I'm going through some machine learning algorithms now and some of the math is just befuddling. </p>
<p>Specifically right now, I'm learning the EM algorithm (expectation maximization) and it seems that there is a large disconnect between what is requi... | 71,033 |
<p>Does anyone know of an approximation for the logarithm of the standard normal CDF for x<0?</p>
<p>I need to implement an algorithm that very quickly calculates it. The straightforward way, of course, is to first calculate the CDF (for which I can find suitably simple approximations on Wikipedia), and then to tak... | 71,034 |
<p>I am looking for a prior for a scale parameter for which I have prior knowledge such that: "$\sigma$ typically does not exceed 100." ("typically" meaning that occasionnally this can happen).</p>
<p>In such a context, I notice in the paper <a href="https://faculty.washington.edu/jmiyamot/bayes/gelmana%20prior%20dist... | 71,035 |
<p><strong>(1)</strong> If I believe my instrument is exogenous conditional upon a few exogenous variables, do I include them only in the first stage? I.e. would the command be: </p>
<pre><code>ivregress 2sls Y (X= inst1 inst 2 exog1 exog2) exog3 exog4
</code></pre>
<p>Where <code>Y</code> is the dependent variable, ... | 71,036 |
<p>I just got comments from a reviewer to a submitted article and didn't understand what I should do very well.
Here are the tests I performed: </p>
<p>We first used principal components analysis (PCA) to ordinate the sites according to topological and physical variables, and to bring out potential shifts in physical ... | 71,037 |
<p>I have come across the famous <a href="http://en.wikipedia.org/wiki/Coupon_collector%27s_problem" rel="nofollow">coupon collector's problem</a>.</p>
<p>Linking the problem to the <a href="http://en.wikipedia.org/wiki/Twelvefold_way" rel="nofollow">Twelvefold way</a>, my first reaction has been to use the case with ... | 71,038 |
<p>This is probably a really dumb question but I can't find the answer anywhere.</p>
<p>I have been given a bunch of data and asked to calculate proportions between two variables. The variables are both counts (this is social science stuff).</p>
<p>The problem is that there are a number of zeroes dotted althrough my ... | 71,039 |
<p>I asked this question on <a href="http://stackoverflow.com/questions/20971480/trying-to-determine-the-similarity-of-the-distributions-of-labels">stackoverflow</a> first since it is more of an implementation question, but I got no answers yet, therefore I'm asking it here again. </p>
<p>I have a dataset which is ann... | 71,040 |
<p>I'm taking the Probablistic Graphical Model course here: <a href="https://class.coursera.org/pgm-003/" rel="nofollow">https://class.coursera.org/pgm-003/</a></p>
<p>This class uses the concept of Factors extensively with regards to graphical models: <a href="http://en.wikipedia.org/wiki/Factor_graph" rel="nofollow"... | 32,321 |
<p>I performed a cluster analysis and now want to consider if the variable “I have a smart phone” (yes/no) significantly differ between the cluster solutions by using chi square test. The p-value was greater than 0.05, so I have to accept the null hypothesis (there is no significant difference between the clusters and ... | 18,336 |
<p>I have an elementary question that I'm sure must be answered in textbooks somewhere, but I haven't found it yet. Why is the average the right way to deal with Gaussian noise?</p>
<p>Let's flesh this out a bit. Here's my model. There is an unknown parameter $\theta$. We have iid random variables $X_1,\dots,X_n$,... | 71,041 |
<p>Suppose I have one time series and two competing models that describe it. Model 1 is ARMA$(p_1,q_1)$, model 2 is ARMA$(p_2,q_2)$-GARCH$(r,s)$. </p>
<p>I obtain AIC values of model 1 and model 2. I would like to conclude that the model with the lower AIC value is the prefered model. However, I am not sure whether I ... | 71,042 |
<p>cty year qtr tl</p>
<p>Argentina 2009 Q4 3</p>
<p>Argentina 2010 Q1 2</p>
<p>Argentina 2010 Q2 7</p>
<p>Argentina 2010 Q3 7</p>
<p>Argentina 2010 Q4 10</p>
<p>Argentina 2011 Q1 7</p>
<p>Argentina 2011 Q2 7</p>
<p>Argentina 2011 Q3 1</p>
<p>Argentina 2011 Q4 7</p>
<p>Argentina 2012 Q1 5</p>
<p>The data set... | 71,043 |
<p>Is there a correct technical name for the group of observations between two quantiles? For example, if you have the values of the four cut-points that divide a population into five groups of equal size, my understanding is that these levels are the quintiles. However, there is often a reference to “quantile means” a... | 32,322 |
<p>AIC (BIC) model selection methods are widely used. These methods can select non-nested models unlike likelihood ratio type selection that requires model to be nested. The AIC has definition $\text{AIC}=-2\text{log}L+2V$ where $L$ is the likelihood of the model and $V$ is the effective number of paramters in that m... | 6,668 |
<p>Can anyone tell me how to judge if a supervised machine learning model is overfitting or not? If I don't have an external validation dataset, I want to know if I can use ROC of 10 fold cross validation to explain overfitting. If I have an external validation dataset, what should I do next?</p> | 35,746 |
<p>The following is a spatial point pattern: <img src="http://i.stack.imgur.com/3NXRG.jpg" alt="enter image description here"></p>
<p>and these are the corresponding Ripley's K function and L function for this data:
<img src="http://i.stack.imgur.com/SsZAs.jpg" alt="enter image description here"></p>
<p><img src="htt... | 71,044 |
<p>Assuming I have a discrete-time Markov chain with only five states. The chain will be used for the prediction of the macroscopic states which are observable and coming from a timeseries. I use maximum likelihood estimation to calculate the transfer probability matrix. </p>
<p>Now I hvae the TPMs and I can plot vari... | 71,045 |
<p>My x and y data (n) have a non normal distribution. I'm measuring the mean of the distribution (I'm using Python):</p>
<pre><code>x_m=np.mean(x)
y_m=np.mean(y)
</code></pre>
<p>I would like to measure error that represent the standard deviation of the mean (from the 16th and 84th percentile). Do you think this is ... | 43,025 |
<p>The (Strong) Law of large numbers states that</p>
<p>$ \frac{1}{N}\sum_{k=1}^N h(X_k) \rightarrow \mathbb{E}\left[h(X)\right]$</p>
<p>a.s in $\mu$ as $N\rightarrow \infty$. </p>
<p>but I can't find any conditions on $h(\cdot)$ other than it needs to be $\mu$-integrable.</p>
<p>I am not overly comfortable with me... | 297 |
<p>Why we need variance in this world?</p>
<p>What is the purpose to make such function and how does it work?</p>
<p>I know that it is a measure of how the data spread, but why we don't just use the absolute variation to solve this problem?</p> | 49,295 |
<p>I wish to analyze the following :</p>
<p>Predictor Variable (IV): Satisfaction of sexual needs as important (4 items scale and respond based on 4 point likert scale. Sum up to get the item score.)</p>
<p>Response Variable (DV): Condom usagae (2 options : never or sometime)</p>
<p><strong>Questions:</strong></p>
... | 71,046 |
<p>The following dataset shows observations (count data) of cedar trees growing in small, medium, or large forest gaps (i.e. openings). You can see that that there is an unequal sample size and normality is questionable. I would like to test the following hypotheses:</p>
<ul>
<li>Ho: Cedar trees grow on all substrat... | 71,047 |
<p>In this article there is a plot of the outlier effect.</p>
<p><a href="http://stats.stackexchange.com/questions/104882/detecting-outliers-in-time-series-ls-ao-tc-using-tsoutliers-package-in-r-how">Detecting Outliers in Time Series (LS/AO/TC) using tsoutliers package in R. How to represent outliers in equation forma... | 458 |
<p>I need to segment a sequence of 0s and 1s by their proportion at relatively large scales. As an example, let's define 5 different states that represent 5 different ratios of 1s & 0s.</p>
<pre><code>Alphabet: 1 and 0
State Definition emission prob.
state 0: 100% zeroes and 0% ones 0:... | 71,048 |
<p>When training a parameterized model (e.g. to maximize likelihood) via stochastic gradient descent on some data set, it is commonly assumed that the training samples are drawn i.i.d. from the training data distribution. So if the goal is to model a joint distribution $P(X,Y)$, then each training sample $(x_i,y_i)$ sh... | 37,501 |
<p>I'm computing some conditional probabilities, and associated 95% confidence intervals. For many of my cases, I have straightforward counts of <code>x</code> successes out of <code>n</code> trials (from a contingency table), so I can use a Binomial confidence interval, such as is provided by <code>binom.confint(x, n... | 71,049 |
<p>Edit: I think this is a better question,
Say, I have categorical characteristics such as gender, race. How should I use Fisher's test and chi-square test?
I was looking at this: <a href="http://math.hws.edu/javamath/ryan/ChiSquare.html" rel="nofollow">http://math.hws.edu/javamath/ryan/ChiSquare.html</a></p>
<p>end... | 32,333 |
<p>I am an economist currently working with this book: <a href="http://darp.lse.ac.uk/papersdb/Cowell_Measuringinequality3.pdf" rel="nofollow">Frank Cowell - Measuring Inequality</a></p>
<p>On page 25 a formulation of the relative mean deviation is given as follows:
$$
M = 2 \left[ F\left(\bar{y}\right) - \Phi(\bar{y}... | 71,050 |
<p>I am VERY new to SEM and AMOS. I ran a model where I obtained 0 DF, so it could not compute the fit. So, I am left to cut out parameters. HOWEVER, I'm not sure where I can cut them in my particular case. I have attached here a screenshot of my model...you can see there are not too many parameters. I am trying to... | 71,051 |
<p>I just fitted a boosted regression coxph model:</p>
<pre><code>cox=gbm(Surv(periods, event) ~ grade + fico_range_low + revol_util + dti, data=notes)
</code></pre>
<p>However, I want to obtain the survival curve from the model similar to the <code>survfit()</code> function in the <code>survival</code> package. Doe... | 71,052 |
<p>I have a situation similar to this:</p>
<p>9 normal-sighted subjects are each tested under two conditions: say, with and without spectacles (of a fixed power) and asked to reach towards an object many times in each condition (approximately 5000 repetitions, but varies with condition and subject). The goal is to mak... | 71,053 |
<p>I have a question concerning the analysis of experimental data.</p>
<p>Imagine the following situation (which I simplify to make the point clearer):</p>
<ul>
<li><p>I ask my participants to give a numerical answer to 3 questions, say, A, B, and C. So in total there are 3 data points per participant.</p></li>
<li><... | 71,054 |
<p>Hi This maybe a basic Stats question.</p>
<p>Let say I have 3 networks of different sizes. Size in terms of number of nodes and links.
Network n1, n2 and n3 have v1, v2 and v3 nodes and l1, l2 and l3 links. That is all we know about the networks.</p>
<p>For each of these networks we compute some parameters based ... | 71,055 |
<p>I know how to do analysis in Decision tree but I am not sure how the data is classified in the output. Is there any criteria there in decision tree for the output? Can I assign the output at what basis we need the data. Please help me to know this.</p> | 32,339 |
<p>I am looking at some data for the risk of mortality in patients undergoing treatment A vs treatment B and I am given the total number of patients in each treatment arm and the relative risk + confidence intervals of mortality. How would I go about finding the actual number of deaths in each treatment arm?</p>
<p>He... | 71,056 |
<p>In Linoff and Berry's "Data Mining Techniques" they mention reducing the number of categorical variables in a classification model by replacing the variable with the historic response rate.</p>
<p>"When building model sets for directed data mining, a powerful transformation is to replace categorical variables with ... | 32,341 |
<p>I have a set of data with summary as below:</p>
<p><img src="http://i.stack.imgur.com/K3fO6.png" alt="data summary"></p>
<p>The data are non-normal and transformations did not obtain normality.</p>
<p>Given the data are continuous I have narrowed the range of distribution down to
'Cauchy','Weibull','Gamma','f','L... | 49,860 |
<p>I have a question regarding how to find an equation for data points that have disturbances. For example, I have the following data:</p>
<ul>
<li>P = 366 measured values </li>
<li>T = 366 measured values</li>
<li>t = [ 1 : 366 ], representing the days of the year (index)</li>
</ul>
<p>So at each t (day), we have va... | 32,343 |
<p>I am currently conducting analyses where I wish to investigate how one variable (M) mediates the association between SES (3-level categorical variable) and a measure of health (continuous variable). The association between M and health is curvilinear, meaning that both low and high levels of M is associated with inc... | 43,062 |
<p>I would like to be sure I am able to compute the KL divergence based on a sample.</p>
<p>Assume the data come from a Gamma distribution with shape=1/.85 and scale=.85. </p>
<blockquote>
<p>set.seed(937) </p>
<p>theta <- .85</p>
<p>x <- rgamma(1000, shape=1/theta, scale=theta)</p>
</blockquote>
<... | 71,057 |
<p>I have fitted a dynamic panel data model with Arellano-Bond estimator in gretl, here is the output:</p>
<pre><code>Model 5: 2-step dynamic panel, using 2332 observations
Included 106 cross-sectional units
H-matrix as per Ox/DPD
Dependent variable: trvr
coefficient std. error z p-value
... | 71,058 |
<p>When I use 5-k cross validation, is the mean absolute error (MAE) equal to</p>
<p>$$\text{mean}(\text{MAEs of each 5 steps})=\frac{1}{5}(MAE_1 + \cdots + MAE_5)$$</p>
<p>or equal to</p>
<p>$$\text{mean}(\text{absolute errors of all predictions})$$?</p> | 32,344 |
<p>I am a PhD student but I am having a hard time understanding certain aspects of statistics.
I just ran an ANOVA and I got no significant interaction effect between Density (0 and 20) and Species (species A and species B). </p>
<p>However, Tukey's test shows that there is a significant difference between these vari... | 32,345 |
<p>I am using three Gaussian distributions with which I generate random numbers to represent many candidate xyz points. </p>
<p>I use some selection criteria (details not particularly relevant) to decide on the final position, but I would like to know what the probability of my final xyz point is, and indeed what th... | 32,348 |
<p>Read something about the Hausman test that didn't sound right in some grad course handout online.</p>
<p>It stated that the Hausman null of OLS and IV not being statistically different, if not rejected, means there is no evidence of endogeneity.</p>
<p>It also states that under the null it is assumed that OLS is c... | 71,059 |
<p>There are well-known HOV tests, for example <a href="http://en.wikipedia.org/wiki/Levene's_test" rel="nofollow">Levene's</a>, <a href="http://en.wikipedia.org/wiki/Brown%E2%80%93Forsythe_test" rel="nofollow">Brown-Forsythe's</a>, <a href="http://en.wikipedia.org/wiki/Bartlett's_test" rel="nofollow">Barlett's... | 71,060 |
<p>My question is not about statistical programming. We know how to code the software in a regression with many independent variables. My question is about how the computer software controls for all variables at the same time mathematically.</p>
<p>Simple correlation of two variables is easy to understand, as each var... | 49,481 |
<p>I have 24 months of sales data by customer and when these customers were touched by different marketing channels (email, coupon, etc). I am trying to build a Marketing Mix Model to show me the baseline sales and the lift by different channels. I know SAS can do this but I am wondering if this can be done in R. Anybo... | 71,061 |
<p>I am confused about the <strong>Vector Error Correction Model</strong> (<strong>VECM</strong>).</p>
<p>Technical background:<br>
<strong>VECM</strong> offers a possibility to apply <strong>Vector Autoregressive Model</strong> (<strong>VAR</strong>) to integrated multivariate time series. In the textbooks they name ... | 71,062 |
<p>Given a very large number of samples $n$ from the population, suppose that I am trying a standard hypothesis test on the means:</p>
<p>$$\begin{align}H_0:&\overline{x}\leq\mu_0\\
H_1:&\overline{x}>\mu_0
\end{align}$$</p>
<p>I am interested in the power of my test as I increase $n$. If I am given nice... | 43,075 |
<p>I have recently been introduced to to Hommel Hochberg corrections. I am trying to find a simple explanation about what this actually is/does, but am having no luck. Can anyone please give a brief and simple description about Hommel Hochberg corrections?</p> | 32,357 |
<p>Baron and Kenny outlined several steps to aid in determining if a mediational analysis is appropriate to test a particular hypothesis. The very first step was <a href="http://davidakenny.net/cm/mediate.htm" rel="nofollow">"Show that the initial [independent] variable is correlated with the outcome [dependent]"</a>. ... | 32,358 |
<p>In <a href="http://stats.stackexchange.com/questions/33566/is-joel-spolskys-hunting-of-the-snark-post-valid-statistical-content-analysis">another question,</a> I asked about the statistical validity of StackExchange's <a href="http://blog.stackoverflow.com/2012/07/the-hunting-of-the-snark/">"Hunting of the Snark"</a... | 6,864 |
<p>I know there are lots of questions/answers about dealing with interaction effects in regressions on this site, but I think there is a need to summarize a bit. I don't know if there is a standard way to deal with it, or if it makes sense. I just want to make a list of occasions when people may see interaction effects... | 71,063 |
<p>I am studying <a href="http://www.holehouse.org/mlclass/07_Regularization.html" rel="nofollow">Andrew Ng's Machine Learning lecture notes</a>. I understand either we can manually choose the number of parameters, or we can use regularization to make it correctly fit.</p>
<p><img src="http://i.stack.imgur.com/XadCK.j... | 71,064 |
<p>I'm not sure that I've titled this question correctly, but here is my query. </p>
<p>Suppose you are given a set of measurements and the uncertainty (variance) associated with each. The task is to statistically figure out how many different objects were likely measured and finally, to combine measurements into a si... | 71,065 |
<p>I have a complete dataset with input variables and response variables. I would like to perform a simulation where I give the input variables and generate randomly the response variables. </p>
<p>Is there a way to do that without using parametric models (like in machine learning), or do I have to find a conditional ... | 71,066 |
<p>I'm trying to get an estimate of average number of days until some event occurs (the event is <strong>guaranteed</strong> to eventually occur). I have some sample where this event has already occured for most observations, so the number of days is known. However, this event has yet to occur for many other observatio... | 71,067 |
<p>I have read Alexandru Niculescu-Mizil and Rich Caruana's paper "<a href="http://aaaipress.org/Papers/Workshops/2007/WS-07-05/WS07-05-006.pdf">Obtaining Calibrated Probabilities from Boosting</a>" and the discussion in <a href="http://stats.stackexchange.com/questions/5196/why-use-platts-scaling">this</a> thread. How... | 71,068 |
<p>My training dataset has 1500 features - all numeric. (But only about 200 data points). I want to create additional features and then use the exhaustive list for feature selection.</p>
<p>For creating additional features, I considered generating all 2-way interactions between the features. I ran the following code i... | 71,069 |
<p>I have a likelihood function of all the data $y$ $$L(\tau ,\theta |y)\propto \theta ^{\sum \delta _{i}^{C}+\sum \delta _{i}^{H}}\tau ^{\sum \delta _{i}^{H}}e^{-\theta \sum x_{i}^{C}-\tau\theta\sum x_{i}^{H}}$$
where $\sum \delta _{i}^{C}, \sum \delta_{i}^{H},\sum x_{i}^{C}$ and $\sum x_{i}^{H}$ are constant,</p>
<p... | 71,070 |
<p>This question is leading on from the following question.
<a href="http://math.stackexchange.com/questions/360275/e1-1x2-under-a-normal-distribution">http://math.stackexchange.com/questions/360275/e1-1x2-under-a-normal-distribution</a></p>
<p>Basically what is the $E\left(\frac{1}{1+x^2}\right)$ under a general Gaus... | 71,071 |
<p>I have three techniques, called A, B and C. Each can be used independently when trying to perform four related tasks (Tasks 1, 2, 3 and 4). I have run lots of tests, trying all combinations of each technique being on or off. My results look something like this. Each number represents how many times the task was comp... | 32,363 |
<p>I have some problem about my model.
my model is based on VAR. (vector auto-.)
well, I've tested ARCH test, BG test(autocorrelation p) and jarque.bera.test.
Model is stable. Also I got good result for ARCH and BG (both fail to reject) but I failed jarque.bera.test. What does it mean?
I know it didn't satisfies white... | 71,072 |
<p>I have a simple question for data transformation for fitting my dataset to a negative exponential graph. There are negative values on my dataset which hinder fitting a negative exponential curve. How can I successfully transform my data in statistical way?
My data is about Mantel correlation coefficients with distan... | 71,073 |
<p>I am taking a regression course that is mainly theoretical. But we are given scatter plots and residual plots, and we are supposed to be able to describe the relationships and interpret them. I find interpretation part difficult sometimes. Is there a good book that has exercises using SPSS output that I can use to ... | 71,074 |
<p>A couple of points that I need cleared up, thanks ahead for any help.</p>
<ul>
<li>In a D dimensional SVM what is the dimension of the maximal separating plane? Intuitively (and following VC logic) it will be D-1, is that correct....</li>
<li>In the derivation of the SVM, what roles do the Lagrangian multiplier pla... | 71,075 |
<p>In the Annals of Statistics paper "Defining the curvature of a statistical problem(with applications to second order efficiency)" by Bradley Efron, he claims the following two statements in the first paragraph.</p>
<ol>
<li><p>The locally most powerful test of $\theta=\theta_0$ versus $\theta>\theta_0$ is unifor... | 47,856 |
<p>I was reading some notes on ML and clustering and it claimed that the run time of clustering was O(kn) where k is the number of clusters and n is the number of points. </p>
<p>I was wondering why this was true and if someone had an analysis for it.</p>
<p>This is what I have thought so far though:</p>
<p>Recall t... | 71,076 |
<p>Given a sample of inter arrival times for an entity at the same location, is there a distribution that can fit such a sample?. I was thinking about poisson, but was concerned about the independence, since the next arrival may be dependent on the previous arrival time. </p>
<p>Or is using a time series approach bett... | 71,077 |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/1444/how-should-i-transform-non-negative-data-including-zeros">How should I transform non-negative data including zeros?</a> </p>
</blockquote>
<p>I want to log-transform some of my data because the Levene... | 49,418 |
<p>I'm trying to find a model to predict a test score (0 to 100) from many independent ordinal variables (all are on a 1 to 10 scale). Since there are SO many ordinal variables, using binary dummy variables would probably be a mess. The test scores are skewed, (as well as many of the ordinal variables) so I'd like to ... | 6,200 |
<p>I am currently facing problems dealing with lots of individual simple correlations (28 individual DTI connections strengths, individual behavioural scores on 31 time points). That would be 28x31 individual correlations. Referring to <a href="http://stats.stackexchange.com/questions/8300/correlation-analysis-and-corr... | 71,078 |
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