question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I have a problem in multivariate time series. The data consist of three time series related to foreign trade. Although my client is still doing research and attempting to find monthly data for all three series, she may only have quarterly data for some series. She has data for 10 years.</p>
<p>I am considering int... | 33,988 |
<p>In my data set, I have 3 covariates ($V_1, V_2, V_3$) and response ($V_4$), generated by a program specifically written to generate random variables using an Inverse Gaussian distribution, in which $ \sigma^2 = 1 $ and $ \mu = \frac{1}{(\beta_0 + \beta_1 \cdot V_1 + \beta_2 \cdot V_2 + \beta_3 \cdot V_3)^\frac{1}{2}... | 46,141 |
<p>There are many models in existence for ordinal $Y$, for example the proportional odds ordinal logistic model, the continuation ratio model, and the cumulative probit model. The first and third of these are in a class of models specifying Prob$(Y \leq j | X) = F(\alpha_{j} + X\beta)$ where $F$ is a non-decreasing fu... | 72,157 |
<p>Could someone point me to an introductory-level explanation (think Wikipedia entry) of what sequential change point detection is?</p> | 72,158 |
<p>I have a data set, total_data and I applied a model to it. For instance, the model has one parameter $\beta$, and I calculated the log-likelihood of the fitted model (using maximum likelihood method). In the mean time, I have a stratification variable that could divide total_data into two subsets: high_risk_data and... | 72,159 |
<p>I have a dataset that contains data from 307 subjects and nine variables for each subject. I would like run a PCA. My problem is that I get a KMO value of 0.06. My question is whether this is due to the fact that within every subject the variables add up to 1. Am I right with this assumption? and is there another wa... | 33,993 |
<p>Background: I am developing a Python Statistics Framework, not because the ones out there are bad but because it will help me learn Python and Statistics. I have taken AP Stats, and read scattered books and articles beyond. I am more than willing to read up on whatever shiny technique will solve my problem: The issu... | 72,160 |
<p>I have a simulation routine that produces measurements of a continuous variable and I also know the true value. What is the optimal method to graphically depict, analyse and present the error or measurement? Any references, links, ideas, hints to the right direction are more than welcomed.</p> | 37,964 |
<p>The upper and lower prediction intervals for the forecast periods are provided by the forecast() function.
However, neither prediction or confidence intervals seem to be available for the fitted values within the range of the actual data.
Why is this?</p> | 72,161 |
<p>in <a href="http://stats.stackexchange.com/questions/47519/load-forecast-model-with-temperature-data">my question</a> on a load forecast model using temperature data as covariates I was advised to use regression splines. This really seems to be a/the solution. </p>
<p>Now I face the following problem: if I calibrat... | 16,618 |
<p>In some resources, I saw that the observed information matrix is the negative of the expected value of the Hessian matrix. However, in some other resources I saw that it is just the negative of the Hessian. Also, in R this is calculated by the inverse of the Hessian matrix (no negative). I am extremely confused. Can... | 72,162 |
<p>Below is the graph of two variables, X and Y, each representing count data. N=348. Note the scales of the axes:<br>
<img src="http://i.stack.imgur.com/ih1yU.jpg" alt="http://i.imgur.com/tNGyTX5.jpg"> </p>
<p>Y is very approximately lognormal, but X has no decent fit (including Poisson, negative binomial, lognormal... | 72,163 |
<p>I am working on a project where I have to do multi-label text classification. I want to understand that whether my approach is correct or I am missing something. I am using R to do it.</p>
<blockquote>
<ol>
<li>Clean the text</li>
<li>Create a corpus. While creating the corpus I am removing the sparse term ... | 72,164 |
<p>I would like some help on how to interpret my results for the <code>polr()</code> function in <code>R</code>- for my ordinal logistic regression.
It is particularly hard to interpret results as there are no p values. I have tried the the standard model-fitting functions, including predict, summary and do not underst... | 34,000 |
<p>I am re-doing an analysis done in a paper <em>Experimental Designs in measuring the effectiveness of promotions</em> where they have fitted a nested ANOVA model to a crossover designed sample </p>
<p><img src="http://i.stack.imgur.com/O372d.png" alt="enter image description here"></p>
<p>In the paper they have fit... | 72,165 |
<p>Firth's penalized maximum likelihood estimates, exact logistic regression and Bayesian logistic regression (e.g. bayesglm) can account for separation in logistic regression. But how to account for probability weights and complex survey designs in these methods (e.g. in R or Stata)? </p> | 294 |
<p>Does the intercept value of a regression equation have meaning in a time series dataset?
Suppose I have a dataset:
the intercept is 27.512, but we are 95 percent sure that the intercept is between -34 and 89.074. Does the intercept value bear meaning?</p>
<p><strong>Statistics using SPSS:</strong></p>
<p><img src... | 72,166 |
<p>I need help for choosing a proper test for inter-rater reliability. I have three raters (experts) who have analysed the quality of images (10 images from different location). The data is ordinal (image quality is assessed numerically from 1 to 5).</p> | 72,167 |
<p>Consider a case when I have data that has $n$ dimensions and I want to transform this data into $n-1$ dimensions.</p>
<p>For this problem in PCA we project all data points to a $n-1$ dimension plane preserving the variance. </p>
<p>If I draw a hyperplane using SVM (that will be a $n-1$ dimension plane) and project... | 72,168 |
<p>This question is inspired by two seemingly equivalent attempts to solve a question asked yesterday: <a href="http://stats.stackexchange.com/questions/67375/in-r-how-to-sample-from-the-output-of-combna-b-if-the-a-choose-b-is-too-lar">In R, how to sample from the output of combn(a,b) if the "a choose b" is t... | 72,169 |
<p>Given a symmetric, positive definite, covariance matrix $S$,
how can I calculate a matrix $C$ such that </p>
<p>$CSC^T$ is the Identity matrix $I$? </p> | 34,004 |
<p>My objective is to actually get to the Standard Error for every point estimate of a linear regression. I originally thought that the Standard Error of a linear regression model was constant. And, that it was simply equal to the square root of the Mean Squared Deviation of the residual. That's why the model's Stan... | 34,005 |
<p>I read some research papers about Lachenbruch methods- 2 parts model. I am a clinician cum researcher and don't have much knowledge/experience in statistics. </p>
<p>We used a scale (St. George's Respiratory Questionnaire) in a study (in general village population in India), 0 indicates no problem and 100 indicates... | 72,170 |
<p>Hi all I am doing a supervised classification of a binary labelled data where I have a mixture of categorical and continuous attributes. I have in total 6 attributes and nearly 6500 instances. I was wondering if there is an expected performance of a classifier based on (bias/variance) that might influence my decisio... | 34,006 |
<p>I am a bit confused as to how to calculate random baseline. If I understand correctly the random baseline is calculated by adding up the squared probabilities of all the classes. The random baseline classifier thus picks a class at random, instead of choosing the most frequent one.</p>
<p>I have 7 classes, each wit... | 72,171 |
<p>I have two vectors $v_1$, $v_2$. Each can have arbitrary values and I measure their correlation. $v_1$ and $v_2$ can also be different in length and I zero-pad the shorter to macht the longer vector length. Shift invariance of correlation allows to find the the shorter within the longer vector.</p>
<p>Sometimes eit... | 72,172 |
<p>I'm using scipy and I'd like to calculate the chi-squared value of a contingency table of percentages. </p>
<p>This is my table, it's of relapse rates. I'd like to know if there are values that are unexpected, i.e. groups where relapse rates are particularly high: </p>
<pre><code> 18-25 25-34 35-44 ... | 72,173 |
<p>If I have a discrete probability distribution $p$ with $K$ classes</p>
<ul>
<li><p>Gini index = $\sum_{K}$$p_k$(1-$p_k$)</p></li>
<li><p>Entropy = -$\sum_{K}$$p_k$log$p_k$</p></li>
</ul>
<p>Per 'The Elements of Statistical Learning',
<code>"Both the Gini index and cross-entropy are lower for the second split. For... | 72,174 |
<p>Until now I thought that the significance level and the confidence interval were the complement of each other, i.e. when some question asked me to carry out a
hypothesis test with a $p %$ significance level I would construct a $(1-p)$ confidence interval and see if it englobes or not the null hypothesis. </p>
<p>Ho... | 34,008 |
<p>I have a k x n dataset where k equals the number of variables and n equals the number of observations per variable. I know these data are correlated and I would like to whiten them with the ordinary whitening transformation. Inconveniently, k outnumbers n by far, so that when estimating the k x k covariance matrix i... | 72,175 |
<p>I was reading this paper related to gaussian processes <a href="http://ipg.epfl.ch/~seeger/lapmalmainweb/papers/bayesgp-tut.pdf" rel="nofollow">http://ipg.epfl.ch/~seeger/lapmalmainweb/papers/bayesgp-tut.pdf</a>. I didn't get how they derived the posterior of the gaussian process given some observed data</p>
<p>I u... | 49,623 |
<p>I work in a company that gathers work environment surveys. When a survey is done we create reports that are handed out to the managers in the company to show where they need to focus their efforts and such.</p>
<p>In these reports we show a comparison of the variance of the calculated group compared to the variance... | 24,753 |
<p>I've been looking for an introductory book in statistics and experiment design for a methods course for psychology students. I think I've been looking through at least 30 books and all go through the same old motions. Fist hypothesis testing, then t-test, Anova, two-Way Anova and ordinary least square regression. An... | 72,176 |
<p>I have various datasets I need to analyse regarding soil properties, all in the same fashion, with one fixed effect (which is a position along a transect, indicating different land uses). Now my main level of replication is across different transects, which will obviously have some form of random variance associated... | 45,055 |
<p>I have administered a questionnaire to respondents asking about customers' adoption of technology. I want to do an exploratory principal components factor analysis in Stata to form constructs from a couple of questions (in line with the existing literature). </p>
<p>The variables that I want to construct are percei... | 72,177 |
<p>I have measured the time taken to solve a problem by algorithm $X$ and by algorithm $Y$. It takes a quite long time, so I have only 10 data for each algorithm:
$$
X : ( x_1, x_2, \dots , x_{10}) \\
Y : ( y_1, y_2, \dots , y_{10})
$$
In my paper I reported the ratio
$$
r = \frac{\sum_{k=1}^{10} x_k }{\sum_{k=1}^{1... | 72,178 |
<p>I am using logistic regression to predict $X \rightarrow Y \in \{0, 1\}$ based on the featurization $\phi(X)$. The training objective function is </p>
<p>\begin{equation}
\mathcal{L} = \sum\limits_{i=1}^{n}{y_i \log \sigma(\theta^\top \phi(x_i)) + (1-y_i) \log (1-\sigma(\theta^\top \phi(x_i))},
\end{equation}</p>
... | 34,012 |
<p>I am just a novice in factor analysis.</p>
<p>I am writing some presentation about factor analysis and I am mainly reading about exploratory factor analysis. </p>
<p>Both EFA and CFA have diagrams. For EFA usually factor loadings are seen on the arrows. However, for CFA usually there are some "1" on some arrows, b... | 72,179 |
<p>When applying the M-step for a mixture of Bernoulli distributions, one of the parameters in our maximization is the Bernoulli parameter $\mu_{k}$, where $k$ is the index of the "mixture component", and
$$
p(x|\mu_k) = \prod_{i=1}^D \mu_{ki}^{x_{i}}(1-\mu_{ki})^{(1-x_{i})}.
$$ In our maximization with respect to thi... | 72,180 |
<p>Are there methods to get the trend of a signal envelope?
An example of signal here :</p>
<p><img src="http://i.stack.imgur.com/jolMw.png" alt="enter image description here"></p>
<p>The black line is the signal, the red lines are what my eye see as the envelope of that signal. I'd like to know what method could be ... | 72,181 |
<p>I am struggling with nls model given below. I have a blur idea how to set up the initial values in it. Shall I use "try and error" method or is there any other way to make it more systematic. </p>
<pre><code>> model3<-nls(H2~H1*(A2^b1*(A1^b1*(b3+H1+sqrt((b3+H1)^2+2*H1*exp(b2)/A1^b1))+exp(b2))/
+ A1^b1*(A2^b1*... | 34,014 |
<p>I work in a chemical laboratory and endeavour to estimate Measurement Uncertainty (MU) from sample retests. The procedure is well established. But what I an dealing with is a set of data where some duplicates are quite legitimate and reflect the underlying MU while others are not as the first test of the pair was... | 34,015 |
<p>In the free online book <a href="https://github.com/CamDavidsonPilon/Probabilistic-Programming-and-Bayesian-Methods-for-Hackers" rel="nofollow">Bayesian Methods for Hackers</a>, the last figure shows the estimation of the expected value of $\lambda$ for any given day:</p>
<p><img src="http://i.stack.imgur.com/jkoAp... | 72,182 |
<p>I'm using the <a href="http://cran.r-project.org/web/packages/kernlab/kernlab.pdf" rel="nofollow">kernlab</a> package in R to build an SVM for classifying some data. </p>
<p>The SVM is working nicely in that it provides 'predictions' of a decent accuracy, however my list of input variables is larger than I would l... | 72,183 |
<p>I have data and I want to assertain whether it is beta or gamma distribution. </p>
<p>Once I know what the distribution is, how do I find out what the parameters are?</p>
<p>btw I am a complete novice</p> | 72,184 |
<p>I am trying to implement SVM and i did my parameter selection(grid search) on the whole data and used the best values of C and gamma from that search to test on the testing data.
Sometimes, the cross-validation accuracy, i get is 100%. Is this method wrong? What is the correct way of doing?</p>
<p>How should i go a... | 45,067 |
<p>CARET is a convenient tool that wraps dozens of modelling methods. CARET allows the user to access performance statistics such as RMSE, confusion matrices, etc. in a generic way without having to recall the usage of various modeling methods.</p>
<p>However, some models have unique reporting outcomes. For example, w... | 72,185 |
<p>I have forecasts and actuals for panel data (i.e. time-series cross-sectional data). The forecasts are already generated and provided by some source outside of R. I'd like to evaluate the quality of the forecasts.</p>
<p>Are there standard tools in R that perform various diagnostics on the residuals? By diagnostics... | 72,186 |
<p>Good afternoon</p>
<p>I am working on a study where the dependent variable (% of people in one ethnic group voting, essentially) and one of the independent variables (% of such people in the population) are measured annually for 10 years. There are other independent variables that are not time dependent.</p>
<p>I ... | 72,187 |
<p>In a Bayesian setting for parameter estimation, what should be the parametric form of the prior distribution in order to perform l2 regularization?</p> | 37,812 |
<p>I am training a large set of neural networks for a quite simple task. 10 of the networks have the same configuration, but have different amount of data. The 10 networks each have one hidden layer, with 2 neurons in it. The first network gets 1.000 training examples, the next 2.000 and the last one gets 10.000 traini... | 72,188 |
<p>My question arises from my current task to develop a clinical prediction model using ordinal logistic regression (with rms), but applies to any kind of regression analysis.</p>
<ol>
<li><p>The proportional odds assumption (difficult to assess...) is only roughly met. (I am aware of the continuation ratio approach).... | 72,189 |
<p>I am working with Fisher Ratio. I compute this ration from a function that was already implemented in the software I am working on. But I would like to be sure that it does what I think it does. <a href="http://www.graphpad.com/manuals/Prism4/RegressionBook.pdf" rel="nofollow">Prism</a> proposes a method for confid... | 72,190 |
<p>I'm an Industrial Engineering Major and I'm looking out for book(s) on Probability and Statistics (Combined would be preferred but separate would do as well) which :</p>
<ul>
<li>I, as a <strong>self learner</strong>, can work with.</li>
<li><p>Is concise but covers : <em>Statistical methods for data analysis. Desc... | 72,191 |
<p>I am not a statistician, but I have a personal project and I need a help.</p>
<p>I will simplify the project a lot to make it more clear and easier to understand. Then in base of your answers, I can fit it to my real project.</p>
<p>Let's say that I have a pot with many balls inside with a number on the balls.</p>... | 36,876 |
<p>I want to make an ANCOVA analysis of data density per plant epiphytes. At first, I would like to know if there is any difference in plant density between two slopes one N and one S, but I have other data such as altitude, canopy openness and height of the host plant. I know that my covariate would have to be the two... | 72,192 |
<p>I am currently assessing some results I have from a model I applied on a corpus of text data I have mined.</p>
<p>My problem is that my professor have told me to use a certain method, and I do not really know how to attack this problem the most sensible way.</p>
<p>The main idea is to assess if there is a relation... | 72,193 |
<p>For an iid sample $X_1, \dots, X_n$, is the rank statistic distribution free? I.e. for each $k$ s.t $1 \leq k \leq n$, will the distribution of the rank of $X_k$ not depend on the distribution of $X_i$? </p>
<p>I think yes. Suppose $X_i$ has a cdf $F$ which admits an inverse $F^{-1}$, then $F^{-1}(X_1), \dots, F^{-... | 34,030 |
<p>I have a multivariate Gaussian for a set of data, and I'd like to compute the confidence interval for that data sample.</p>
<p>In hopes of finding an elegant solution, I did an eigendecomposition and transformed the data into the basis defined by the eigenvectors where the eigenvalues are the variance of that dimen... | 24,763 |
<p>I am interested in multivariate investigations. I have been trying to learn about designing such experiments where there is one dependent variable (a class/group) and many independent variables that ideally would help discriminate between the groups. However, the 'basic' issue I am running into is the problem of sam... | 34,032 |
<p>I'm working at an online agency, where we run a lot of AB testing in order to test differences in proportion between two groups (test vs. control). Standard practice in the industry for testing difference of proportions is either based on the normal distribution or chi-squared.</p>
<p>Chi base $\lambda$ tests tend ... | 36,877 |
<p>Does anyone know what exact data cleaning steps one need to undertake in order to clean data for a logit regression (not a logistic regression)?</p>
<p>I have only time variables, meaning year and month, as my independent variables, and I am using R.</p>
<p>A logit regression is simply a normal linear regression w... | 72,194 |
<p>I have been confused by two separate questions (Stock & Watson - introduction to econometrics ch.3), using different values for standard errors.</p>
<p><strong>The first:</strong> In a survey of 400 voters, 215 respond to vote for the incumbent, 185 for the challenger. Let p denote the fraction of all likely vo... | 72,195 |
<p>I want to ask about response rate. I have distributed 2500 posts. However, I have received back around 30. Then, I sent 200 posts as reminders with appealing letter. I have received one or two only. The total usable questionnaires: 21.
After a while, I determined that I need to send by email. Therefore, I sent over ... | 72,196 |
<p>I have subdivided the globe into 100 sq mile bins and then collected how many tweets were sent with a geolocation within each bin. At first I color coded each bin on the map based off a standardized value of (tweetInBin)/(maxTweetInAnyBin). This produced only one "hot spot" with all the other places being almost uni... | 72,197 |
<p>I'm trying to perform a power calculation with G*Power.</p>
<p>There are two quite important options, the meaning of which is not clear to me:</p>
<p>"Number of groups" - what is this? I have a 2x2 repeated measures factorial design. Does this mean there are four groups, or, as the rest of the internet suggests, i... | 46,842 |
<p>I'm trying to estimate a bunch of bimodal distributions, i.e. two means and two standard deviations, based on a variable number of inputs. If no input is present, a constant value should be returned. From my anecdotal knowledge of what Bayes is about, this should be exactly it, no? Adapt a prior based on incoming ev... | 46,437 |
<p>I have correlated data points and they are fitted with a trend line. I wanted to know how far these points lie away from an arbitrary 1:1 line (45 degree line with data of equal magnitude). Is there any test to find how significant it is away from this 1:1 line?
Thank you</p> | 72,198 |
<p>I've got some categorical data where each observation has multiple attributes, and I want to make a probabilistic model of this using Dirichlet distributions. For example, in the two dimensional case I would have two attributes A, B having n, m distinct values respectively, and then I would have a Dirichlet distribu... | 36,878 |
<p>I'm trying to analyze a general game. This is probably well-known, in which case pointers to relevant literature would suffice (but explanation would not be declined!). If it's not standard, of course any help would be appreciated, even if short of a full answer.</p>
<p>Suppose I have N objects (say, 100) with nont... | 46,448 |
<p>Can a Random Forest be trained to appropriately predict count data?
How would this proceed? I have quite a extensive range of values so classification doesn't really make sense. If I would use regression would I simply truncate the results? I'm quite lost here. Any ideas?</p> | 46,450 |
<p>I am stuck with the definition of a regression model regarding the inclusion of a constant averaged by the dependent variable.</p>
<p>I have a dataset <code>M=(id, x1,x2,x3,x4)</code> where: </p>
<pre><code>id: is the id of the product
x1: is a continuous variable denoting price (0 to 999 USD)
x2: is a categori... | 72,199 |
<p>I was wondering about the motivation behind the following definition of expected loss:</p>
<p>$$E[L] = \sum_{k} \sum_{j} \int_{R_{j}} L_{kj} p(x, C_{k})dx$$</p>
<p>where $L_{kj}$ is the loss matrix, in which $j$ is the predicted class and $k$ the true class, $R_{j}$ is the decision region corresponding to the $j$ ... | 45,080 |
<p>A project I am working on currently is to create a heart beat sensor using a finger plethysmograph. It returns a signal to my ucontoller that only includes positive peaks. For example, the ideal signal it will sent to my ucontroller would be</p>
<pre><code>1 1 1 5 1 1 1 5 1 1 1
</code></pre>
<p>Where the numbers r... | 72,200 |
<p>What would be the best approach to choosing the multi-class strategy (MSVM, OVA, ECOC) for classifying a large number of classes with limited examples of each class? </p>
<p>Another two factors that define the solution, in my case: </p>
<ul>
<li>The probability of prediction is an important factor that decides t... | 46,456 |
<p>Can anybody help me with a continued fraction representation of the multivariate normal distribution? Such a representation is well-known for the univariate case; see, for example,</p>
<blockquote>
<p>C-I. C. Lee. <a href="http://www.ism.ac.jp/editsec/aism/pdf/044_1_0107.pdf" rel="nofollow" title="here">On Laplac... | 72,201 |
<p>I have data with a few thousand features and I want to do recursive feature selection (RFE) to remove uninformative ones. I do this with <a href="http://cran.r-project.org/web/packages/caret/index.html" rel="nofollow">caret</a> and RFE. However, I started thinking, if I want to get the best regression fit (random fo... | 72,202 |
<p>I'm doing a project related to identifying sales dynamics. My database contains 26 weeks after launching the product (so 26 time-series observations equally spaced in time). </p>
<p><img src="http://i.stack.imgur.com/Dquwy.jpg" alt="http://imageshack.com/a/img18/5628/l5qg.jpg"></p>
<p><img src="http://i.stack.imgu... | 20,797 |
<p>To reduce the confusion, I changed my application from traffic to meeting room, so this application is about modeling a meeting room efficiency , the data collection is built by placing a kind of motion sensor at the center of room for detecting and counting the motion activities. So my data are time-series based fo... | 72,203 |
<p>I've been doing some work on modeling aspects of a sales process, where each in-progress sale is referred to as an Opportunity. I'm trying to develop a model to predict when an Opportunity will close (doesn't matter if it's lost or won).</p>
<p>A given Opportunity has several descriptive characteristics, such as th... | 72,204 |
<p>I am learning R and data analysis methods, so I apologise if my question is too basic. I have a data sample of 4K+ records of sociologic survey. There are a few demographic variables and a lot of yes/no type categorical questions. There is a binary variable I am trying to predict based on the categorical questions ... | 72,205 |
<p>I am trying to implement Linear Discriminant Analysis for face recognition. I have 3 classes and each classes have 10 image each. The dimension of matrix in class A, B and C is 10*500 .So each row will represent an image</p>
<p>If I find the mean matrix of each class I am getting dimension of 1*500. That is I will ... | 16,887 |
<p>Given two confidence bands, it seems natural to consider the confidence band of the product of these two distributions. Does this have a name? Are there any reference that might be helpful regarding this notion?</p>
<p>Edit: Assume that the errors of the first, say, regression curve are not correlated with the erro... | 49,890 |
<p>I am going to estimate False Discovery Rate using permutation tests. </p>
<p>To my knowledge, several R packages are applicable for multiple testing. </p>
<p>I have several independent datasets for meta-analysis. </p>
<p>I computed a Pearson correlation coefficient, converted it into a Fisher-Z score and then cal... | 72,206 |
<p>I have a problem: y~x1+x2+x3+x4 where the response variable y is always more than or equal to the explanatory variable x1 (for e.g. x1 represents the income of one person in a couple and y is the overall income of the couple). It seems that normal linear regression is inadequate in this case. What kind of regression... | 16,899 |
<p>I am a master's student, and I need your help. I did experiment on one group of rats, the group was tested during 8 days, this is the first stage. The same group was also tested again but this time the test phase was 7 days. I tried to do my analysis using ANOVA repeated measures but I had a problem with the days. I... | 49,303 |
<p>The pi-lamda theorem states that if $Q$ is a pi-system contained in a lambda system $L$, then the sigma-algebra generated by $Q$ is also contained in $L$. We can use this to show that the CDF completely determines the distribution of a random variable, but I do not understand the connection. </p> | 72,207 |
<p>I have different groups of dolphins, some with offspring, some without. I'll count how many types of vocalizations were emitted by each group, and want to find out if there is a statistical difference between groups with and without offspring.</p>
<p>My dataset is something like:</p>
<pre><code>Group_number Voc... | 72,208 |
<p>Subitization is the rapid, accurate enumeration of low-numerosity displays, distinguished from
counting by a sharp non-linearity in the plot of response times. Below is a representative plot, from Watson, D. G., Maylor, E. A., & Bruce, L. A. M. (2007). Notice that mean enumeration times for displays 1-3 increas... | 34,051 |
<p>I've been reading up a bit on eigenfaces. I think I understand the basic concept of it - vectorize a set of facial images then reduce the dimensionality of the images using PCA. What I don't really understand it the visualization of the lower-dimensional representation of the images. In the facial images, the num... | 72,209 |
<p>So, with the help of someone here in stats i could solve most of my problems.</p>
<p>Now i'm stuck at this part:</p>
<p>I have the below code, which worked very well if this values were fixed.</p>
<pre><code>immediate.amput.below.EV
watchful.wait.EV
</code></pre>
<p>Now what they are is vectors. They represent ... | 72,210 |
<p>As title, is there anything like this? I know how to calculate CI for arithmetic mean, but how about geometric mean? Thanks.</p> | 72,211 |
<p>morning, say i have 5 wheat varieties undergoing 2 treatment. when counting the seeds of the replicates the percentage difference between the means of the 2 treatments is 10% for variety 1, 30% for 2, 50% for 3, 80% for 4 and 90% for variety 5. </p>
<p>how could i demonstrate that var 1 has a significantly greater... | 72,212 |
<p>I am fitting a binomial family glm in R, and I have a whole troupe of explanatory variables, and I need to find the best (R-squared as a measure is fine). Short of writing a script to loop through random different combinations of the explanatory variables and then recording which performs the best, I really dont kno... | 34,055 |
<p>I have a survey analysis data in which responses for various independent questions range from 'Poor' to 'Excellent'. Belown is the scorecard for these responses:</p>
<pre><code>Excellent 100
Very good 90
Good 75
Fair 25
Poor 0
</code></pre>
<p>There were also some blanks present in the survey data ... | 72,213 |
<p>I am investigating the effect of a drug on EEG and cognition in epilepsy patients.
We have done EEG and neuropsychological (NP) tests twice, before and after medical treatment.
Some of parameters in EEG and NP tests were significantly altered after drug treatment (done by Wilcoxon rank sum test, as the distribution ... | 45,097 |
<p>Let A be $n \times p$ matrix of independent variables and B be the corresponding $n \times 1$ matrix of the dependent values. In ridge regression, we define a parameter $\lambda$ so that: $\beta=(A^\mathrm{T}A+\lambda I)^{-1}A^\mathrm{T}B$ .
Now let [u s v]=svd(A) and $d_{i}=i^{th}$ diagonal entry of 's'. we define... | 72,214 |
<p>While testing type I error rate using R, I found that I am getting higher than 5% false positives with a 2-way ANOVA.</p>
<p>However, I thought one of the reasons for using an ANOVA (as opposed to multiple tests) was to control the type I error. So, what am I doing wrong?</p>
<p>Here is the R code:</p>
<pre><code... | 34,057 |
<p>I have what I naively thought to be a fairly straight forward problem that involves outlier detection for many different sets of count data. Specifically, I want to determine if one or more values in a series of count data is higher or lower than expected relative to the rest of the counts in the distribution.</p>
... | 45,100 |
<p>I have been doing supervised learning and classification with multilayer perceptron for some time. But now I need to use unsupervised learning to infer the presence of a pattern and I would need some help. It is not a hard problem by itself and I can solve it by supervised learning (by showing "examples" of the poss... | 72,215 |
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