question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I'm working on generating a weighted linear model in R using the <code>lm</code> function. My dataset has about 1200 observations. My independent variables are a set of 168 principal components, i.e., the independent variables have already been normalized and are uncorrelated. There are no factor variables. The weig... | g60376 | [
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<p>From the Johnson's book, I can see the orthogonal factor model is as follows:</p>
<p>$X-\mu=LF+\epsilon$</p>
<p>So if I use SPSS for extracting factor scores from a factor analysis of several variables, then am I going to get factor scores for mean subtracted variables? Actually my intention is to use the factor s... | g16433 | [
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<p>Does there exist any reference thesaurus for statistics and machine learning terms? I know that Wikipedia articles often contain synonyms, but I would like to have a mere thesaurus that I could go through easily (vs. a full encyclopedia) to make sure I know all the jargon.</p> | g60377 | [
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<p>The normal distribution is a prerequisite for ANOVA. It is not clear what we are supposed to understand by "standard normal distribution". Does ANOVA need a <em>standard</em> normal distribution? The answer can be given in the context of meta-analysis of sample correlation.</p> | g33963 | [
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<p>Is there a way to quantify \ test \ describe how likely it is that high dimensional data come from a single Gaussian or a mixture of Gaussians (with different means \ SDs) or not?</p>
<p>What I am thinking of is similar to the idea of a t-test, but when the separation into groups is unknown. </p> | g60378 | [
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<p>I have recently begun exploring R
I have downloaded a data set that contains flight times for when a plane takes off at Origin and Lands at destination
The data has up to three months’ worth of information and looks something like this</p>
<p>Plan_ ID, Origin_Airport, Destin_Airport, Sched_Dep, Sched_Arriv, Act... | g60379 | [
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<p>Users arrive according to Poisson process with rate $\lambda$. If every third user is removed, then do the remaining users form a Poisson process with rate $2\lambda/3$?
If every other user is removed, then do the remaining users form a Poisson process with rate $\lambda/2$? and so on..?</p> | g16438 | [
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<p>I saw the following graph today in the Atlantic (<a href="http://www.theatlantic.com/business/archive/2014/05/its-expensive-to-be-poor/361533/" rel="nofollow">link</a>),
but I can't understand how the cost of televisions can go decrease by more than 100 percentage points in the last ten years.
How is that mathematic... | g60380 | [
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<p>Work out the autocorrelation</p>
<p>$r_Y(\tau) = E[Y(t)Y(t+\tau)]$</p>
<p>with
$Y(t) = \int_{-\infty}^{\infty} h(t-u) x(u)$
and
$X$ a WSS, ergodic process</p>
<p>I always get: $h(t)* h(t+\tau) * r_X(\tau)$ (with $*$ convolution)</p>
<h2>My approach</h2>
<p>(after multiplication)</p>
<p>$\int h(t-u) ( \int h... | g16440 | [
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<p>I'm looking for ways to test for "cumulative advantage" effects in a longitudinal dataset (see image)</p>
<p><img src="http://i.stack.imgur.com/W3LQ2.jpg" alt="Data set example"></p>
<p>I guess the data set is principally similar to this: <a href="http://www.caldercenter.org/whatis.cfm" rel="nofollow">http://www.c... | g60381 | [
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<p>Is there a book or a review article serving as a good general reference to <a href="http://en.wikipedia.org/wiki/R%C3%A9nyi_entropy" rel="nofollow">Rényi entropy</a>, its applications and related concepts?</p> | g16441 | [
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<p>I am trying to classify a set of $p$ predictors into 5 classes. But my sample size $n$ is rather small, so I fear I won't get a very robust estimate.</p>
<p>Now an idea would be to subset my data for each of the 5 response classes, and simulate more data in each class. I would e.g. assume a multivariate normal dist... | g16442 | [
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<p>Can anyone please tell me the difference in training and testing of a model. I have developed 5/6 different single pass online learning algorithm (ets, ets+, evolving fuzzy modelling, SOFNN, Gustafson-Kessel, participatory learning). I have collected 3000 pts of data for training and 500 points of data for testing f... | g60382 | [
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<p>Suppose I have a data frame like this (four groups, for each n = 12):</p>
<pre><code>> head(my_data,n=8)
Subject Group Condition Value
1 1 A Cond_1 12.40407
2 1 A Cond_2 14.89856
3 2 B Cond_1 13.87088
4 2 B Cond_2 14.31305
5 3 C Cond_1 13.40773... | g16444 | [
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<p>-----EDIT:
Sorry, I was somewhat in a hurry when I wrote my question. Let me rephrase it.</p>
<p>I intend to conduct a Mixed ANOVA analysis consisting of a Repeated Measures DV and a between-subjects IV (a categorical variable that has three conditions). In order to draw the right conclusion I would first like to d... | g50 | [
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<p>At first I was under the impression that latent variable models and graphical models were different things altogether, but after reading some papers about the former class of models, it seems they have more in common than I thought. For instance, in both cases there's a specification of the conditional probabilies. ... | g40526 | [
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<p><a href="http://stats.stackexchange.com/questions/22648/understanding-no-free-lunch-theorem-in-duda-et-als-pattern-classification?newreg=0dd0bbb181484e418e77988f89d41bb8">Please see this question regarding Duda, Hart, and Stork's No Free Lunch Thm Discussion</a></p>
<p>Hi all, I was having trouble understanding the... | g16447 | [
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<p>Currently, I am looking for methods to calculate some kind of price sensitivity index for customers of an online store based on the purchase histories. I've found a lot of literature in which panel data was used to calculate the price elasticities for a certain product (category) first, and then a regression model w... | g60383 | [
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<p>The photo below is an example of the result i would like to obtain using the test which i cannot find in the article itself, i was hoping maybe any of you would know. I have tried to carry out chi square test for goodness of fit but what i really want is to able to compare BP between two groups (men vs. women). Woul... | g60384 | [
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<p>I Conducted a study in some patients it included:</p>
<ol>
<li>age</li>
<li>gender</li>
<li>duration</li>
<li>some medical tests</li>
<li>pre. and post questionnaire</li>
<li>post test results</li>
</ol>
<p>I divided the patients into two groups acoording to duration of complain
I need to correlate these two grou... | g21231 | [
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<p>I lack some knowledge in the concepts of parameters, estimates and moment (math and stats). I can't find an online easy-to-understand source of information about these concepts. Would you help me with a link or even better with a speech ?</p>
<p>Here is one thing that I'd aimed to understand:</p>
<p>Source: a book... | g60385 | [
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<p>I've searched around a bit, but am having trouble finding an answer to my specific question that isn't too technical. </p>
<p>I want to predict the probability that we are at a turning point – arbitrarily defined – for a given time series. I have historical data from which I have determined some times that are "tur... | g16450 | [
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<p>My textbook on cross-validation is Element of Statistical Learning (Hastie et. al., 2nd ed.) In sections 7.10.1 and 7.12, they talk about the difference between conditional test error $E_{(X^*,Y^*)}[L(Y, \hat{f}(X))|\tau]$ and expected test error $E_\tau [E_{(X^*,Y^*)}[L(Y, \hat{f}(X))|\tau]]$.
Here $\tau$ is the tr... | g27922 | [
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<p>I have a simple neural network and it works with the logistic function as activation function. Now I want to avoid the saturation problem by substituting the logistic function by the hyperbolic tangent:</p>
<pre><code>#define SIGMOID(x) (1.7159*tanh(0.66666667*x))
#define DSIGMOID(S) (0.666666667/1.7159*(1.7159-(S... | g60386 | [
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<p>I have a dataset with $\approx2000$ entries (for example, model of car).</p>
<p>For each car model I know the weight of the car, and the power output. I don't know the price or age, which is likely to affect the power to weight ratio of the car. I have a reasonable amount of faith in the data, but some manufacturer... | g16452 | [
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<p>I am looking for a tutorial type example that shows the step by step process sampling from a simple hierarchical model. </p>
<p>For example, I am trying to study the distribution of <code>p</code> in a Bernoulli experiment where I have a set of 10 data / observations (<code>h[i]</code>).</p>
<pre><code>model {
... | g60387 | [
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<p>I'm working on a binary classification problem for which the dataset is mostly composed of categorical features, but also a few lexical ones (i.e. article titles and abstracts). I'm experimenting with Random Forests, and my current strategy is to build the training set by appending the $k$ best lexical features (cho... | g16454 | [
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<p>How can I best analyze the presence/absence data that I have gathered about the <a href="https://en.wikipedia.org/wiki/Illuminated_manuscript" rel="nofollow">illuminations</a> in a medieval manuscript? I have identified individual motifs in chapter headings and created a spreadsheet that has 1 or 0 for each (there a... | g60388 | [
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<p>How do you prove that</p>
<p>$X_n - E[X_n] = O_p(\sqrt{Var(X_n)})$</p>
<p>It's used in my textbook and I don't know where they get it from.</p> | g16457 | [
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<p>Currently, I am using a neural network to classify data into one of three groups (a logistic activation function is used on all but the output nodes). I can train the neural network in two ways:</p>
<p>1) For each observation $X_{i}$ I can have one output variable $O_{i}$ that can take three values: $1,2,$ or $3$.<... | g60389 | [
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<p>In CS294A lecture notes, Andrew Ng writes (about autoencoders): "Usually weight decay is not applied to the bias terms... Applying weight decay to the bias units usually makes only a small different to the final network, however". </p>
<p>Is there any particular reason for which we shouldn't apply weight decay to t... | g60390 | [
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<p>I am confused by the behaviour of ks.test (package stat) a) in the presence of ties and b) if one-sided while doing a two-sample test. Documentation: "Exact p-values are not available for the two-sample case if one-sided or in the presence of ties."</p>
<p>I ask if black (experiment) and red (control) follow the sa... | g60391 | [
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<p>Suppose we want to model the temperature ($1$ = hot, $0$ = cold) of 5 regions over the following time periods: 1 month, 6, months, and 4 years. Suppose a predictor variable is $X$ (amount of deforestation, 1 = a lot, 0 = very little). In modeling the main effect (deforestation), should we include time as a predictor... | g60392 | [
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<p>I don't know if this is a suitable question here. I have data from 2 groups, neutral and positive.</p>
<p>Here how the data looks like</p>
<pre><code>A 02.840 00.960 00.950 00.995 00.995 00.602 1
B 04.730 01.000 01.000 00.999 01.000 01.000 1
C NULL 00.970 00.005 00.078 00.987 00.000 0
D ... | g16461 | [
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0.048170045018196106,
... |
<p>I and my friends just had a little discussion whether the events are independent or dependent if they have no outcome in common. I thought that they have to be independent. When two events are independent, then $P(A)=P(A\mid B)$. Is the information given in the question enough to establish this?</p>
<p>If you look ... | g60393 | [
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<p>I am working on Lasso problem and the selection of the optimal tuning parameter with $k$-fold procedure, say $k=10$.
Since this procedure relies on random subsampling, value of the optimal parameter will change each time I repeat the procedure. As an example, it can be 0.32, then 0.41, then 0.29, etc.</p>
<p>Two qu... | g45960 | [
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<p>*<strong><em>Background:</em>*</strong>
I am doing an academic study that is more exploratory in nature (my advisor did not want me to develop any hypothesis). So I read books and conducted interviews to try and gather a large list of items that people feel are important and influential to the topic being studied. F... | g45961 | [
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0.0225... |
<p>Please pardon my ignorance, but...</p>
<p>I keep finding myself in a situation, where I'm faced with a bunch of new data I managed to find. This data usually looks something like this:</p>
<pre><code>Date Number1 Number2 Category1 Category2
20120125 11 101 Dog Brown
20120126 21 ... | g45962 | [
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<p>I have an array of $n$ real values, which has mean $\mu_{old}$ and standard deviation $\sigma_{old}$. If an element of the array $x_i$ is replaced by another element $x_j$, then new mean will be</p>
<blockquote>
<p>$\mu_{new}=\mu_{old}+\frac{x_j-x_i}{n}$</p>
</blockquote>
<p>Advantage of this approach is it requ... | g49771 | [
0.008822356350719929,
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<p>Please, this is maybe a meta-statistics question but let me ask this. What would you tell a mathematician to answer the question:</p>
<p>"Mention few examples what kind of data analysis the insurance companies or banks do?" Something a la "They have the set of claims and compute the mean."...
(obviously a stupid e... | g60394 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/20514/books-for-self-studying-time-series-analysis">Books for self-studying time series analysis?</a> </p>
</blockquote>
<p>I am new to time series modelling altogether. But I am aware about regression mod... | g49467 | [
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0.0119070... |
<p>My new computer clock runs at a rate that changes in odd steps over time, even after I tuned it via the Linux adjtimex software. Here is a plot of the change in the cumulative clock drift for each of about 1700 samples taken every 10000 seconds, with a bunch of missed points and outliers when I was off the network ... | g60395 | [
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<p>Is there a standard way to test whether two vectors were drawn with the same <strong>discrete</strong> distribution in R? Something like a Kolmogorov-Smirnov test, but for discrete distributions. I think two-sample chi-squared test would be appropriate. Does any package provide it? I can't get <code>chisq.test</code... | g9771 | [
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<p>Suppose I have a set of sample data from an unknown or complex distribution, and I want to perform some inference on a statistic $T$ of the data. My default inclination is to just generate a bunch of bootstrap samples with replacement, and calculate my statistic $T$ on each bootstrap sample to create an estimated di... | g49783 | [
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<p>If an item follows normal distribution, average also follows normal distribution. What about minimum and maximum?</p> | g1010 | [
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<p>I have 3 different groups: A, B, and C:</p>
<ul>
<li>A (has a medical condition) has 30 entries </li>
<li>B (another medical condition) has 31 entries </li>
<li>C (control group) has 55 entries</li>
</ul>
<p>All participants have information on the same set of variables.</p>
<p>I want to assess whether there is a... | g45996 | [
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<p>I have two IVs that are highly correlated with each other at 0.979 (Pearson) & 0.919 (Kendall's).</p>
<p>IV1: Quality of response<br>
IV2: Quality of Technical Advice</p>
<p>Sample Size: 252</p>
<p>Considering the similarity in the phrasing of the IVs, could it mean that the respondents do not perceive a diff... | g60396 | [
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<p>I have a contingency table computed from the out of sample observations. In some cases not all classes are represented in the out of sample and hence do not appear. I want to coerce the contingency table to report zeros for classes not in the out of sample. How can I do it efficiently. For example my contingency tab... | g60397 | [
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<p>I'm using OpenANN to train a neural network with one hidden layer and a softmax output layer with cross entropy as the error function. For my application, the conjugate gradient algorithm seems to be a good performing algorithm compared to for example LBFGS.</p>
<p>The image below shows the training error and valid... | g60398 | [
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<p>I'm trying to detect subpopulations of data in a set of data. The problem is that the data may have more than one subpopulation and the subpopulations may not be normally distributed. For example, the data could look like this....</p>
<p><img src="http://i.stack.imgur.com/98yw9.png" alt="enter image description h... | g60399 | [
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<p>With a paired sample t-test I found out that participants communicated more pride about a team achievement than about an individual achievement.</p>
<p>What I would like to examine now, is if this difference between communicated pride about a team achievement and an individual achievement is larger for Indians comp... | g16478 | [
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<p>I am learning exploratory statistical testing methods in R. Specifically I am trying to learn single variable linear regression. I was hoping that someone would be able to give an explanation of the info that is given as output. Disclaimer: I am a beginner in statistics and not that well versed so I apologize for ... | g49310 | [
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<p>I am fitting a model in the frequency domain, and my fit looks as follows:</p>
<p><img src="http://s3.postimg.org/8aop8zepv/fit.jpg" alt="Model fit"></p>
<p>As you can see, the model function does not fit the data perfectly, especially in the higher frequencies. So, I examined the residuals and found that a polyno... | g60400 | [
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... |
<p>Some time ago when I took a Pattern Classification class, the "concept" was introduced as Multiple Discriminant Analysis: You want to project your data onto a subspace (if you are interested in dimensionality reduction) that yields a better separation between different classes (e.g., in a supervised class. task with... | g60401 | [
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0.018... |
<p>I am running a logistic regression model in R using multiply imputed data created using Amelia II, which I am then analyzing using Zelig. I would like to be able to report some measures of goodness-of-fit (e.g. likelihood ratio, pseudo R-squared, Hosmer-Lemeshow), however none are provided in the default Zelig outpu... | g16481 | [
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0... |
<p>Is there a way to estimate an ARMA equation using the <code>lm()</code> function in R without using <code>arima()</code>?</p> | g60402 | [
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0.045... |
<p>Should the process of feature normalization/standardization be done before or after the feature selection process?</p> | g16483 | [
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0.007830552756786346,
0.015... |
<p>We are working with panel data. But we want to study only the cross-section part of the panel data. So can anybody please tell me how to do any kind of data transformation, so that I can remove the time-series variance from the panel data?</p>
<p>Thank you.</p> | g16489 | [
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<p>Say I have a dataset with several continuous and categorical variables, and I want to identify what variables (values or properties of these variables) may cause one of the continuous variables to increase. How can I model this problem?</p>
<p>Several approaches come to mind (e.g. <strong>logistic regression</stron... | g60403 | [
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0.057807132601737976... |
<p>Suppose I have fitted a Poisson GLM to model rates as follows: </p>
<pre><code>> fit.1=glm(response~X1+X2+ offset(log(population)),family=poisson,data=...)
</code></pre>
<p>I can get the estimated rates by using two new values for X1 and X2 and population=1 as follows:</p>
<pre><code>>new.data=data.frame... | g60404 | [
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-0.01488951314240694,
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0.026294991374015808,
0.028702709823846817,
-0.0... |
<p>i am currently reading Diebold and Li's 2006 paper: Forecasting the term structure of government yields where the authors fit, albeit simple, AR(1) models on clearly non stationary data.</p>
<p>Why is this allowed in certain situations? and what are the consequences/implications of doing so?</p>
<p>Thanks</p> | g21557 | [
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0.02912677265703678,
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0.04065408930182457,
... |
<p>I'm using infer.net for implementing a dynamic Bayesian network model. every node in each layer is dependent on all nodes in previous layer (we want to train wji, the weights of edges between each node j from the previous level (time t-1) to node i in current level (time t)). node values are shown by yi (value of no... | g60405 | [
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-... |
<p>PredictionIO is good to be enough for content discovery and recommendation but it seems it does not support classification. Then I should use a different tool then Prediction IO for my prediction server. Do you know good alternatives?</p>
<p>I know Google Prediction Server, Azure ML, BigML and looking for more alt... | g60406 | [
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<p>I am reading the following paper:</p>
<p><a href="http://www-biba.inrialpes.fr/Jaynes/cc07s.pdf" rel="nofollow">http://www-biba.inrialpes.fr/Jaynes/cc07s.pdf</a></p>
<p>and cannot seem to figure out how Jaynes is deriving (P2) and below (specifically the log arithmetic log[f(x)/f(0)]....) </p>
<p>Can someone help... | g16494 | [
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<p>There is a four category classification system for individuals with HIV, labeled Stages 1, 2, 3, and 4, with higher stages indicating more advanced disease. Cell count is a continuous variable, and you are interested in comparing mean cell count between those in different stages.</p>
<p>My question is how does the ... | g49586 | [
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<p>I have a rather basic question about <a href="http://research.microsoft.com/en-us/um/people/cmbishop/downloads/Bishop-PPCA-JRSS.pdf" rel="nofollow">Probabilistic Principal Component Analysis</a>, which I am now trying to apply to a real-world problem. </p>
<p>In PPCA, the crucial assumption is that the generating p... | g60407 | [
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<p>I'm looking for a paper which I hope exists, but don't know if it does. It could be a set of case studies, and / or an argument from probability theory, about why using cross-sectional data to infer / predict longitudinal changes may be a Bad Thing (i.e. is not necessarily so, but can be).</p>
<p>I've seen the mist... | g60408 | [
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<p>I want to compare the frequency of retweets between 2 groups of unequal size. I've got the total tweet count and the retweet count for each user. I was hoping the R Cookbook webpage would help but the tests presented there seem to be more suited for repeated measures and equal sample sizes for the two groups: <a hre... | g60409 | [
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<p>Let's say I have two experiments of the same type, where I measure something x times in one location and y times in another location, is there any point in looking for a dependency in values between these two experiments? In case it matters, there's a difference in sample size and both samples have a near normal dis... | g16499 | [
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<p>I have a dataset that I have been running one-way repeated measures ANOVA on. The people I am working with are interested in answering how much of an actual change in a measurement would have to happen in order for that change to be considered statistically significant. </p>
<p>So the way to measure the smallest de... | g60410 | [
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<p>The log likelihood is as follows:</p>
<p>$nln\beta + (-\beta-1)\sum ln(x_i)$</p>
<p>Dividing the log likelihood by n gives,</p>
<p>$ln\beta + \frac{(-\beta-1)}{n}\sum ln(x_i)$</p>
<p>Using these two log likelihoods, I got the same MLE estimator, which is $\frac{n}{\sum ln (x_i)}$. However, I was confused by the ... | g16502 | [
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<p>I have number of seeds fallen at different distances. I need to know which model fits these data, if any model does. There are different models that have been used to fit these data: negative exponential, Weibull, lognormal. I need to know how to fit all of them in R, starting from 0, generating the data. I only man... | g60411 | [
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<p>Suppose I have a dataset that was sampled from a mixture of Gaussians: $$ X \sim \sum_i w_i \mathcal{N}(\mu_i, \Sigma_i)$$</p>
<p>Technically, I can center and then whiten $X$ so that it has zero mean and unit covariance. But something about that process seems unsatisfactorily oversimplified: for example, what if t... | g60412 | [
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<p>I would like to get a better intuition for a cost function of an optimisation problem. The cost function depends on a number of real-valued arguments. I would like to find out if the cost function is convex.</p>
<p>Obviously I can visualise the cost function for 2 arguments in a 3-dimensional plot. I did this for a... | g16504 | [
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<p>Consider the constraint optimization $\text{argmin}_{\beta}(f(\beta)+\lambda g(\beta))$ can someone define $\beta(\lambda)$. That is, what is the relationship between $\lambda$ and $\beta$?.</p> | g60413 | [
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<p>Simple linear regression in MATLAB. Something is wrong with my p-values. Stata reports that the p-values should be 0.000 and 0.207, whereas my code reports that they should be 0.0001 and 0.2988. All other statistics are the same as Stata's output. Please help me see the error of my ways.</p>
<pre><code>%number of o... | g60414 | [
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<p>Assume I tracked the behavior of users when they visit a Website. In detail I track the movement from which site to site they click within the Website. So I have a lot of tuples with (userID, site, time). Now I want to visualize if there are any patterns or clusters for the movement. Let's say most of the users clic... | g60415 | [
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<p>Based on an earlier question I balanced the classes such that the numbers in both classes is about similar.
The random Forest gives next result:</p>
<pre><code>> print(rFresult)
Call:
randomForest(formula = finresfh ~ ., data = rFdatasubset, importance = TRUE)
Type of random forest: classificat... | g60416 | [
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<p>Based on results of Null model, some scholars suggest variance attributed to group level and individual level is computed using variance component output, whereas other suggest going the standard deviation scores. </p>
<p>Is there consensus how to calculate ICC?</p> | g343 | [
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<p>I am interested in whether or not a "correlation" of three variables is something, and if what, what would this be?</p>
<p><em>Pearson product moment correlation coefficient</em></p>
<p>$$\frac{\mathrm{E}\{(X-\mu_X)(Y-\mu_Y)\}}{\sqrt{\mathrm{Var}(X)\mathrm{Var}(Y)}}$$</p>
<p>Now the question for 3 variables: Is ... | g60417 | [
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<p>I've trawled the internet looking for R packages to compute the confidence intervals for the mean of a Poisson distribution using the different methods cited by Patil and Kulkarni in their papaer "comparison of confidence intervals for the Poisson mean: some new aspects", REVSTAT vol. 10, no. 2, June 2012, pp 211-22... | g60418 | [
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<p>We know non-zero measurable transformation of a dependent sequence is dependent.</p>
<p>I want to ask if a non-zero measurable transformation of a sequence which is not martingale difference is not martingale difference?</p> | g60419 | [
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<p>This is a fairly complex question so I will attempt to ask it in a fairly basic manner. </p>
<p>I have data on the abundance of 99 different species of estuarine macroinvertebrate species and the sediment mud content (0 - 100 %) in which each observation was obtained. I have a total of 1402 observations for each sp... | g49742 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/11691/how-to-tell-if-data-is-clustered-enough-for-clustering-algorithms-to-produce-m">How to tell if data is “clustered” enough for clustering algorithms to produce meaningful results?</a> </p>
</... | g49587 | [
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<p>I'm using fourth root (<code>1/4</code>) power transformation on my response variable, as a result of heteroscedasticity. But now I'm not sure how to interpret my regression coefficients. </p>
<p>I assume that I would need to take the coefficients to the fourth power when I back-transform (see below regression outp... | g49681 | [
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<p>I have a set of observations which translates into $N_1(x_1,x_2,x_3,x_4)$ points where $x_1,...,x_4$ represent 4 parameters associated with each point. For example, the observed data would look like:</p>
<pre><code>#x1 x2 x3 x4 # <-- Observ
1.2 0.5 46 10 # <-- 1
0.2 8.9 20 13 # <-- 2
0.8 4.5 18 9 ... | g16510 | [
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0.0013825363712385297,
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... |
<p>I would like to know how you would set the parameters for the GBM model?</p>
<p>1)
I could optimize the parameters sequentially. At first, using a large value for shrinkage and a small number of iterations (for faster computation), I would try to optimize n.minobsinnode, interaction.depth, bag.fraction, etc.
Then ... | g60420 | [
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<p>I have a problem with SEM claiming to be saturated where it actually should test for missing covariances </p>
<p>I am running a SEM composed in the following way. The ones with “2” behind are quardratic terms </p>
<p>SEM1 = "
d_birds ~ Q1 + MAT + MAP + TS + VelT + SamplingEffort + NetworkSize + plantp+ MAP2 + TS2... | g60421 | [
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<p>The <a href="http://www.riskglossary.com/link/cornish_fisher.htm" rel="nofollow">Cornish-Fisher Expansion</a> provides a way to estimate the quantiles of a distribution based on moments. (In this sense, I see it as a complement to the <a href="http://en.wikipedia.org/wiki/Edgeworth_expansion#Edgeworth_series" rel="n... | g16512 | [
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<p>I want to perform an OLS regression on time series data using heteroskedasticity robust standard erros.
So far i can come up with this:</p>
<pre><code>model <- lm(I(y[2:T] - y[1:T-1]) ~ y[1:T-1])
regress <- coeftest(model, vcov=vcovHC(model, type = "HC0"))
</code></pre>
<p>Biscally this seems to work but whe... | g60422 | [
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<p>It seems that lots of people (including me) like to do exploratory data analysis in Excel. Some limitations, such as the number of rows allowed in a spreadsheet, are a pain but in most cases don't make it impossible to use Excel to play around with data.</p>
<p><a href="http://www.pages.drexel.edu/~bdm25/excel2007.... | g60423 | [
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<p>I am currently working on a model which takes two parameters and produces a measurement statistic. Think of it as Z = f(X,Y). </p>
<p>Z is a matrix of my statistics and I am creating a surface plot of it in matlab. Basically, I am looking for a mathematical/analytical way of determining if the surface is smooth, or... | g16514 | [
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0.0854131430387497,
-0.0... |
<p>I would like to analyze effect of a treatment on my patient samples by MANOVA in R. I have measurement of 3 different protein level for treated and untreated patients. Now I would like to analyze effect of my treatment on the whole different protein measurements and not each individually (sort of summing them up tog... | g21707 | [
-0.036451615393161774,
-0.04189615696668625,
0.004752821754664183,
-0.02004714123904705,
-0.015323002822697163,
-0.02268579602241516,
0.017093099653720856,
0.08753461390733719,
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-0.007421328220516443,
-0.04391247034072876,
0.004169217310845852,
0.0011099184630438685,
... |
<p>I see that both functions are part of data mining methods such as <a href="http://scikit-learn.org/stable/modules/generated/sklearn.ensemble.GradientBoostingRegressor.html" rel="nofollow">Gradient</a> Boosting Regressors. I see that those are seperate objects. But how is the relationship between both in general?</p> | g60424 | [
-0.00017578215920366347,
-0.008702732622623444,
-0.02820531278848648,
0.005368764046579599,
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-0.036999721080064774,
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0.062235791236162186,
0.... |
<p>I am running a regression where I regress return of a stock on the market return. There is a specific date in my sample on which some event occurred. I believe the effect of this event to last only on that date. I want my model coefficients to be free of this effect because I want to predict what the return would ... | g60425 | [
0.04281162843108177,
-0.03397509455680847,
0.010271262377500534,
-0.04058689996600151,
0.0019820777233690023,
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0.01200913917273283,
-0.05121001973748207,
0.0011481627589091659,
0.07344015687704086,
0.012078815139830112,
0.0084... |
<p>I am performing a physical experiment where the unavoidably inaccurate setup likely creates errors in the inversion of the data for the model.</p>
<p>Let's assume a linear relationship between data $\mathbf d$ and model $\mathbf m$ as follows: $$\mathbf d = \mathbf W \mathbf m,$$ where $\mathbf W$ is the operator (... | g60426 | [
0.012832365930080414,
-0.04379330575466156,
-0.024733509868383408,
-0.013018373399972916,
0.05850886180996895,
0.024484384804964066,
0.03162634000182152,
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-0.07402267307043076,
0.0038494598120450974,
-0.00007605188147863373,
0.02302556112408638,
-0.03905978426337242,
... |
<p>I work with CSV files containing 10-minute data of temperatures of some years of a station, and I usually perform some calculations: mean, average, correlations between two stations, correlations in different seasons, correlations day/night, ...</p>
<p>I program this calculations by using plain Python or Microsoft ... | g60427 | [
0.02474951557815075,
-0.025249890983104706,
-0.0027375714853405952,
0.002562109613791108,
-0.030566656962037086,
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0.013674094341695309,
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-0.034112926572561264,
0.028146957978606224,
-0.017346685752272606,
0.02247851900756359,
0... |
<p>I am running a Gibbs sampler for Multivariate Normal times Inverse Wishart posterior distribution with missing data imputation step.
I am trying to check if my step of simulating covariance matrices from Inverse-Wishart converges. How would I go about it?
In MCMC I usually run Gelman-Rubin diagnostic test. </p>
<... | g46057 | [
0.03780529648065567,
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0.001990750664845109,
-0.05691719800233841,
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0.03766913339495659,
0.011715109460055828,
0.013940846547484398,
-0.013435560278594494,
... |
<p>When I estimate a difference in differences model with two time periods, the equivalent regression model would be</p>
<p>a. $Y_{ist} = \alpha +\gamma_s*Treatment + \lambda d_t + \delta*(Treatment*d_t)+ \epsilon_{ist}$</p>
<ul>
<li>where $Treatment$ is a dummy which is equal to 1 if the observation is from the tre... | g16519 | [
-0.03261832892894745,
-0.03378048911690712,
-0.017562150955200195,
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-0.017282942309975624,
-0.053953152149915695,
0.02703683078289032,
0.01075790822505951,
0.02... |
<p>I have a moderated mediation model with a strong mediation effect, but with confusing results for the moderating effect (using PROCESS). Although the interaction effect in the regression model is insignificant, the conditional indirect effect does show that the mediated effect is conditional on the moderator (values... | g60428 | [
-0.03052520751953125,
-0.013154558837413788,
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-0.0476604700088501,
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-0.022581646218895912,
-0.04086487367749214,
-0.022194931283593178,
0.06235158443450928,
0.03... |
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