question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I am running Pearson's correlation on an overall sample of 400 respondents. </p>
<p>When I isolate male and female responses, my sample becomes 220 male responses and 180 female responses. </p>
<p>If I further isolate male and female responses by (say) age groups, some sample sizes become as low as 35 responses (f... | 33,320 |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/3038/testing-hypothesis-of-no-group-differences">Testing hypothesis of no group differences</a> </p>
</blockquote>
<p>Suppose I have $k$ samples from 2 independent experiments (service times by 2 methods) ... | 49,879 |
<p>This is a bit more "think about it" question - but I see it as an important one to ask.</p>
<p>I have been struggling for the past few days with having a more reproducible-research-like workflow. I am confused with the two different strategies for writing a report.</p>
<p>The two strategies are:</p>
<ol>
<li>Swe... | 71,710 |
<p>How many lags should be used for ACF or PACF displaying if we have $S$ seasonality?</p>
<p>For example,</p>
<p>for 500 observations I have 25 lags<br>
for 200 observations I have 22 lags</p>
<p>It is independent from frequency of seasonality (for $S = 7, 14, 50, 60, ...$ number of lags on the picture is the same)... | 71,711 |
<p>I have collected data to estimate a parameter and am now puzzled about how to generate confidence intervals:</p>
<p>Setup: </p>
<p>1) We have a bag with $N$ coins.<br>
2) Each coin $i \in N$ has a <strong>known</strong> probability of $q_i$ for being picked from the bag.<br>
3) Each coin $i \in N$ has an <strong>u... | 71,712 |
<p>I have carried out a study on change of call volume over a year (oct 07-mar 09). What statistical test on SPSS software can I use to show the difference in call volume on a day by day basis and on a monthly basis?</p> | 33,323 |
<p>Some clustering algorithms require independence of variables but (especially working with real data) variables are often highly correlated.</p>
<p>I have been suggested to apply a Principal Component Analysis to solve the problem (using the resulting linear combination as input for the clustering). But such a solut... | 71,713 |
<p>Is there any difference among the following terms or they are same?</p>
<ol>
<li>Bias </li>
<li>Systematic bias</li>
<li>Systematic errors</li>
</ol>
<p>If there exist some differences then, please explain them. Can these errors be reduced when one increase the sample size?</p>
<p><strong>UPDATE:</strong>
My fie... | 33,325 |
<p>The Gumbel distribution has the general form:
$$F(y)=\exp\left({-\exp{\left(-\frac{y-\mu}{\sigma}\right)}}\right), \quad y\in \mathbb{R}$$
where $\mu \in \mathbb{R}$ and $\sigma >0$. Let $W_1,...,W_n$ be random variables with that distribution and iid. I want to find good estimators for $\sigma$ and $\mu$. What w... | 71,714 |
<p>I have a data set containing daily temperatures <strong>T</strong> at several stations and am interested only in whether <strong>T</strong> crosses a certain threshold or not. In the end, I want to answer e.g. the question: "If <strong>T</strong> crosses the threshold at stations 1 and 2, the probability of <strong>... | 71,715 |
<p>I am now looking for a GLMM, which could fitted a Poisson distribution with a log-link. From what I see until now, <strong>lme4</strong> allow to specify the family and the link function for <code>lmer()</code> model, but the <code>lme()</code> function in <strong>nlme</strong> package doesn't. Is there another way ... | 33,327 |
<p>I have seen that it is possible to perform multi label classification using a binary combination of classifiers or reducing a multi label classification to a multi class classification problem by transforming the tags, and in fact this question has been posed around many times. However, I was unable to find anything... | 71,716 |
<p>Good evening all,</p>
<p>I am doing a self-study exercise, but have been quizzed by a part of the question on finding percentage points of a normal distribution. I fully understand the first part of the question and was able to find the answer, which corresponds to the answer provider.</p>
<p><img src="http://i.st... | 71,717 |
<p>I need to fit a neural network to my data.</p>
<p>I used SPSS 21, but I think it's model summary isn't sufficient.</p>
<p>I also used R (nnet & neuralnet), it has a poor report and I can't find a good model summary for it.</p>
<p>The last one is NeuroSolutions, I used it. very bad! I can't run a model. What a... | 71,718 |
<p>I'm trying to get a handle on interactions between three variables in a regression-sense and how they differ from interactions in an information theory sense.</p>
<p>Imagine we wish to determine whether two factors X and Z are interacting in the context of Y.</p>
<p>For the mutual information based-measure, we use... | 33,332 |
<p>I often use the reduced chi squared as a quick goodness of fit test when fitting histograms. Is there an analogous method that works more generally for interpreting the absolute value of the best fit likelihood when data are not normal? I'm thinking of binomial and poisson with noise here but the more general the be... | 33,333 |
<p>I am supposed to find parameters of individual gaussians in a 1D mixture with a known number of components. I use my own implementation of EM algorithm; however, I am not able to find the right solution.</p>
<h3>Data</h3>
<p>Number of points: 5057<br/>
Number of components: 5</p>
<p><img src="http://i.stack.imgur... | 71,719 |
<p>If any of you would like to confirm if my understanding is correct or wrong,<br> I will be most grateful.</p>
<p>I have done an independent-samples t-test (two-tailed),<br>
for difference between women/men how they see their own skill sett.</p>
<p>In short: <br>
group women,n 76: mean 3,20 - std .980 <br>
group me... | 33,334 |
<p>I have read three main reasons for standardising variables before something such as <code>Lasso</code> regression:</p>
<p>1) Interpretability of coefficients.</p>
<p>2) Ability to rank the coefficient importance by the relative magnitude of post-shrinkage coefficient estimates.</p>
<p>3) No need for intercept.</p... | 71,720 |
<p>I'm using 'betareg' package in R to perform beta regression. predict() function with se.fit=T is supposed to return standard errors along with the prediction but it doesn't. Is there any other way I can get the standard error outputs?</p>
<p>I'm open to using other packages that can perform beta regression too.</p> | 33,336 |
<blockquote>
<p>Consider the communication network shown in the figure below and
suppose that each link can fail with probability <strong><em>p</em></strong>. Assume that
failures of different links are independent:</p>
</blockquote>
<p><img src="http://i.stack.imgur.com/nC10Q.jpg" alt="enter image description h... | 71,721 |
<p>I'm trying to determine the best model for a regression problem between Elastic net regression and a neural network model based on the mean squared error.When I'm fitting the data to the elastic net I do not perform any scaling on the targets, but for the neural network model the target values are scaled to be in th... | 71,722 |
<p>If $X \sim Laplace(\mu, b)$ and $\mu = 0$ such that $X \sim Laplace(0,b)$, it becomes a form of the exponential family. Unfortunately, one source tells me that it becomes $|X| \sim exponential(b)$, another source says that $X \sim exponential(\frac{1}{b})$, and my notes say that $X \sim exponential(b)$. </p>
<p>Can... | 30,871 |
<p><img src="http://i.stack.imgur.com/PILnh.png" alt="enter image description here"></p>
<p>Someone asked what was his probability to win in this situation?</p>
<p>This is an interesting problem and I'll be curious to know an efficient solution.</p>
<p>So far, I wanted also to generalize, with a simplification, we c... | 71,723 |
<p>I looked at a test group (West Coast pop) versus a control group (non West Coast) and took independent samples pre-message and post message for each group. I measured awareness (top-3 box of a 5-pt scale) for each of the 4 independent samples. </p>
<p>I looked at lift (in percentage points) for test group and lif... | 71,724 |
<p>I am considering MCMCglmm as an alternative to MLwiN. The former package works perfectly fine, but I cannot figure out how to model heteroskedasticity at level one. For instance, if I have the following model, individuals within countries</p>
<pre><code>Fixed: y = 1 + x1 + x2
Random Level 2: 1 + x1 (country level)... | 33,343 |
<p>What is an acceptable phrase for reporting a Fisher's exact test where the number of rows and the number of columns are both $>2$. An example in R:</p>
<pre><code>> x <- as.matrix(data.frame("A"=c(10,4,6),"B"=c(45,2,6),"C"=c(23,4,20),
row.names=c("df1","df2","df3")))
> x
A B C
df1 10 45 2... | 71,725 |
<p>I have a set of patients that I split into two parts using some obscure algorithm (doesn't matter how): let the $X$ take on values $A$ and $B$. Each patient belongs to exactly one of 5 disease subtypes: let $S$ take on the values $a, b, c, d, e$. Here is the contingency table:</p>
<pre><code> A B
a 116 ... | 41,471 |
<p>I am having a serious issue trying to figure out why my degrees of freedom are screwy when running my proc mixed model. I have nested data for a MLM analyses, but SAS isn't providing the correct df and I'm not sure why.</p>
<p>I have 50 individuals with 3 or 4 time sensitive datapoints each. Measuring their physi... | 71,726 |
<p>I need to explain the intuition behind what ANOVA is doing to a non-technical person. Is there a visual that explains the idea? A visual that illustrates the key idea in the context of a one-way ANOVA with perhaps 3 factor levels might be helpful?</p>
<p>Let us suppose that the person has taken some statistical cou... | 41,486 |
<p>If I understand correctly, the coefficient of a covariate <code>X</code> under a Weibull accelerated failure time (AFT) model is related to the <code>log(hazard ratio)</code> of the Cox proportional hazard (PH) model in the following way: </p>
<pre><code>d1 = -c1/shape.gamma
</code></pre>
<p>where <code>d1</code>... | 71,727 |
<p>I have two glm, one with a gaussian distribution and identity link and one with gamma family and log link. The predictors are the same, the only thing that change is the response that in the gaussian glm is log-transformed and in the gamma glm is not.</p>
<p>The deviance is lower in the second model, and when plott... | 49,880 |
<p>There are several R packages for Bayesian analysis, i.e., <code>RBugs</code>, <code>JAGS</code>,<code>MCMCPack</code>. Are there any pros and cons for each of these packages? </p> | 49,881 |
<p>I am currently conducting a two-way ANOVA on a dataset and have noticed how significance and F values change dependent on the type of ANOVA I use in R. Why is this?</p>
<p>For instance, if I run a two-way ANOVA the factor I am analysing becomes outputs F (1,28) = 7.2, P <.05.</p>
<p>When I run it by itself howe... | 33,348 |
<p>In my experiment, I compare the resistance of 12 different seed types to seed beetles. I have 30 replications (i.e. 30 times a single beetle larva developing in a single seed) for each variety and assess whether an adult beetle emerges from the seed or not.
The resulting two-way table I analyzed using logistic regre... | 33,350 |
<p>I have two measurements $x_1\pm s_{x_1}$ and $x_2 \pm s_{x_2}$. The error intervals ($\pm$ one standard deviation) do not overlap. Does this necessarily mean that these are two samples from normal distributions with different means?</p>
<p>Or should I run a test to exclude (to some degree) the fact that they might ... | 71,728 |
<p>Are these merely stylistic conventions, or are there substantive differences in the meanings of these notations?</p>
<p>Are there other notations meaning "<em>the probability of</em>" that should be considered in this question?</p> | 71,729 |
<p>I have data aggregated at state level. When I estimate a spatial autoregressive model such as
$$y = \rho W y + X\beta + \epsilon$$ on this data, I see that the autoregressive parameter $\rho$ is moderately significant ($\rho = 0.2$, $p$-val$= 0.06$).</p>
<p>But I am preparing to apply this estimated model to data a... | 71,730 |
<p>The references I can find on HAC procedures (like Newey-West) in regression focus on the standard error of the estimated regression coefficients and hypothesis testing involving the same. I cannot find any references where the HAC estimate of error covariance is used in a generalized least squares procedure to get '... | 33,352 |
<pre><code>library(caret)
set.seed(1)
x <- data.frame(runif(10),runif(10))
y <- rnorm(10)
rfeModel <- rfe(x,y,rfeControl = rfeControl(functions = lmFuncs))
</code></pre>
<p>returns:</p>
<blockquote>
<p>Error in { : task 1 failed - "undefined columns selected"</p>
</blockquote>
<p>While this code:</p>
<p... | 71,731 |
<p>There's a community wiki at: <a href="http://stats.stackexchange.com/questions/170/free-statistical-textbooks/174#174">Free statistical textbooks</a> that has a nice list of freely available textbooks on statistics. Many of the textbooks that people suggest have exercises at the end of each chapter which is great, b... | 71,732 |
<p>I have two measures from each of 20 studies. Random-effects meta analysis has been performed for each of the two measures, and for each measure I have two values to indicate data variability, cross-study (random effect) variance $\tau^2$ and its chi-square test statistic $Q$. Now I'd like to compare the cross-study ... | 71,733 |
<p>Just want to know the ways to remove skewness from the skewed population. I am working on logistic regression (in the insurance domain) for finding out the repurchase propensity of existing users. Income data is right skewed. Will it cause any problem for runing logistic regression? If yes then how to remove it (d... | 71,734 |
<p>Good morning all,</p>
<p>I'm working on a project related to the occupations that university graduates are likely to go into. I have a large data set (N in the hundreds of thousands) where the unit of analysis is an individual person. For each person, I have two categorical variables - a code representing the field... | 71,735 |
<p>I'm in the process of designing a system. </p>
<p>So basically, every day users on my site rack up points based on their activity on my website. So whatever they do on my website, they rack up points.</p>
<p>So on 8/3, a user might do multiple things on my website so that they rack up 10 points.</p>
<p>Every day,... | 71,736 |
<p>Assuming a dataset with the following attributes:<br>
<code>Date</code> (truncated), <code>f1</code> ... <code>fn</code>, <code>#impressions</code>, <code>#goals</code>.</p>
<p>The problem: I want to grow <strong>$n$ trees</strong> that would find the optimal selection of features and their ranges in each, and that... | 20,554 |
<pre><code> The SAS System 14:11 Thursday, October 6, 2013 1
The ARIMA Procedure
Name of Variable = ln_G_S_Index
Period(s) of Differencing 1
... | 6,365 |
<p>The Likert scale I am analyzing has both positive and negative questions, but all the items are answered with 4 - strongly agree, 3 - agree, 2 - disagree and 4 - strongly disagree. For analysis, should I make the weight of the answers the same? </p>
<p>For example, if the statement is positive, then 4 must be given... | 71,737 |
<p>I need a bit help for interpreting this results...</p>
<p>I did a correlation analysis with R with the assocstats function.
The result is: </p>
<pre><code>$summary
Call: xtabs(formula = ~MH[, i] + MH[, j], data = MH)
Number of cases in table: 2306
Number of factors: 2
Test for independence of all factors:
Ch... | 71,738 |
<p>I have a large dataset from which I want to perform a bayesian probit regression using Gibbs sampling <a href="http://www.jstor.org/discover/10.2307/2290350?uid=3738016&uid=2&uid=4&sid=21104089937577" rel="nofollow">1</a>. Since the dataset has one milion rows, and variables from a truncated normal must ... | 71,739 |
<p>As my previous questions I'm trying to solve a problem with my stocks tests.
I tried Breusch-Pagan test for heteroscedasticity but some residuals still pass these tests.</p>
<p>My procedure is:</p>
<ul>
<li><p>Get two stocks prices (I have a matrix with two columns that represent the price lists)</p></li>
<li><p>I... | 49,767 |
<p>I conducted a study in which I collected the height, width, and weight of individuals from 9 different races (i.e I collected 10 to about 30 samples per race).</p>
<ul>
<li><p>How can I can display the distribution of the data for each group for a given variable (e.g., height)? I have thought of using histogram but... | 33,364 |
<p>Is it 'normal' to have two Pearson correlation coefficients which are statistically significant on their own but <strong>not</strong> when compared with each other.</p>
<p><strong>Example</strong></p>
<ul>
<li>r=.9083 (n=45) for females who buy ice-cream and yoghurt </li>
<li>r=.8382 (n=60) for males who buy ice-c... | 44,316 |
<p>I have one dependent variable and many predictors, and I need to use a multiple regression model (linear).
Now, I performed a stepwise regression to determine which independent variables to include in the final model.
However, I see that when results are published, people usually show more than one model. For insta... | 71,740 |
<p>I have a rather large collection of text documents categorized into about 150 categories. While some categories are represented by several thousands of documents, others have only a few hundreds assigned to them. Now I would like to construct a balanced corpus from this data, where each category is represented by th... | 37,907 |
<p>I can't thank the experts enough for their clarifications. One final question following my earlier posts on forming coomposite variables <a href="http://stats.stackexchange.com/questions/13757/how-do-i-weigh-several-variables-at-two-levels-to-create-an-overall-composite-var">here</a>, <a href="http://stats.stackexch... | 71,741 |
<p>I have a regression with two continuous predictors and one dichotomous predictor in Model 1 and two interactions of each of the continuous predictors with the dichotomous predictor in Model 2. The coefficient for one of the interaction terms is significant. However, the F test is not significant (neither for Model ... | 49,368 |
<p>I would like to make a heatmap with row clustering based on cosine distances. I'm using R and <code>heatmap.2()</code> for making the figure. I can see that there's a <code>dist</code> parameter in <code>heatmap.2</code> but I cannot find a function to generate the cosine dissimilarity matrix. The builtin <code>dist... | 33,367 |
<p>I have a huge matrix (individuals X features with row.names as individuals numbers) and the corresponding segment in another vector of 1D (row.names are the same as in my huge matrix and the vector represent the segments associated).
I.E. :</p>
<pre><code>row.names VAR1 VAR2 VAR3 VAR4 … VAR3000
12 4 12 ... | 71,742 |
<p>I want to conduct a linear regression (in matlab) using rolling monthly returns; the aim is to give me a prediction for the next monthly rolling period return. </p>
<p><em>return calculation</em>:</p>
<p>$$\mbox{return}(t) = \dfrac{\mbox{Price}(t) - \mbox{Price}(t-30)}{\mbox{Price}(t-30)}.$$</p>
<p><em>regression... | 33,370 |
<p>Recently I had done some analysis of the effects of reputation on upvotes (see the <a href="http://stats.blogoverflow.com/2011/08/04/does-jon-skeet-have-mental-powers-that-make-us-upvote-his-answers-the-effect-of-reputation-on-upvotes/">blog-post</a>), and subsequently I had a few questions about possibly more enlig... | 71,743 |
<p>Does anyone know how I can find/calculate an overall p-value for a GLS multiple regression model (made with nlme)?</p> | 71,744 |
<p>I am searching for [free] software that can produce nice looking graphical models, e.g. </p>
<p><img src="http://i.stack.imgur.com/QXAmU.png" alt="enter image description here"></p>
<p>Any suggestions would be appreciated.</p> | 44,738 |
<p>I recently measured how the meaning of a new word is acquired over repeated exposures (practice: day 1 to day 10) by measuring ERPs (EEGs) when the word was viewed in different contexts. I also controlled properties of the context, for instance, its usefulness for the discovery of new word meaning (high vs. low). I ... | 71,745 |
<p>I have a data set that includes the number of visits to a website. Here are some descriptive statistics for my data</p>
<p>Median: 4<br>
Mean: 14.1352<br>
SD: 121.8119 </p>
<p>Clearly, there are some huge values (individuals who have visited the site thousands of times.) To remove these outliers I considered simp... | 33,372 |
<p>I am trying to view the output from the GBM package for boosted trees in R. Below I am fitting a single tree without any sampling in order to compare the tree to the complete dataset. First, create the data set:</p>
<pre><code> set.seed(1973)
############## CREATE DATA#############################################... | 33,373 |
<p>I ran principal components analysis in R on my data. All my regressors are continuous, non categorical variables, except gender which I excluded. I will add it and compare model 1 = PCA to model 2 = PCA + gender and see if its significant. </p>
<p>I determined that PC1/2/3 determine 95% of the variance so I only co... | 12,843 |
<p>How does one approach the problem of modeling a "birth-death process" where the arrivals are dependent on the current state in the following way: if the population is above a certain point, the probability of an arrival decreases.</p>
<p>Basically, I'm interested in complicating (slightly) an existing model of "bir... | 44,327 |
<p>I have data which has several properties (metadata, as key value pairs, where the keyspace is shared over the whole dataset) per object.</p>
<p>I took a sample of objects and divided them in n groups according to an unknown algorithm.</p>
<p>What statistical methods or algorithm exists to find the relevant proper... | 71,746 |
<p>I'm curious about why we treat fitting GLMS as though they were some special optimization problem. Are they? It seems to me that they're just maximum likelihood, and that we write down the likelihood and then ... we maximize it! So why do we use Fisher scoring instead of any of the myriad of optimization schemes ... | 71,747 |
<p>Are there any formal tests for heteroscedasticity for non-normal data? I want to run the test on time series logged returns, so would it be okay to assume a linear relationship? To me it makes intuitive sense that the greater the return (rise or fall in price) the greater the variance.</p> | 33,376 |
<p>I have a couple of questions regarding to the interpretation of LMM:</p>
<p>Question 1: If I have three independent factors and two of them have three categories, I will have to run at least four models to see every angle of it, am I right?</p>
<p>For example, I have color (red, blue, green), group (group1, group2... | 71,748 |
<p>I have multiples lists which are ordered. How do I generate a final list with all elements in all lists ranked by their cumulative rank? I.e. the <code>Final</code> column here:</p>
<p><img src="http://i.stack.imgur.com/3eMdD.png" alt="Global ranking of multiple ranked lists"></p>
<p>I can't obtain the data with t... | 33,378 |
<p>There's a distinction that's tripping me up with mixed models, and I'm wondering if I could get some clarity on it. Let's assume you've got a mixed model of count data. There's a variable you know you want as a fixed effect (A) and another variable for time (T), grouped by say a "Site" variable.</p>
<p>As I underst... | 33,379 |
<p>I am trying to match the outputs of PROC REG with PROC GENMOD. I ran a sample test on the 'iris' dataset of R.</p>
<p>The data set is as follows (150 rows in total):</p>
<pre><code> Sepal.Length Sepal.Width Petal.Length Petal.Width Species
1 5.1 3.5 1.4 0.2 setosa
2 4.9... | 33,384 |
<p>What is the difference between discrete data and continuous data?</p> | 71,749 |
<p>When doing a simple random sample to estimate population mean for some statistic, how do I know whether sampling happens with or without replacement?</p>
<p>It feels wrong to use replacement, because 1) my AP stats teacher never does that and 2) I might use someone's data <em>twice</em> in the average.</p>
<p>But ... | 71,750 |
<p>Suppose I have an estimator which includes an indicator function in the objective function, then the objective function is not smooth. But if I want to approximate the behavior of this estimator in small samples I would need to have a certain number of higher order derivatives such that I can apply the usual approxi... | 71,751 |
<p>Any help would be greatly appreciated.</p>
<p><strong>Problem:</strong>
I need help to better understand the probability scores that come from the result of a decision tree model. Specifically, I'm using the gbm package from R to create Generalized Boosted Regression Models, but the results I see are common across... | 71,752 |
<p>I am going through the <code>DPpackage</code> in <code>R</code> which provides functions for <code>non-parametric Bayesian</code> modeling. I am particularly looking at the function <code>HDPMdensity()</code> which relates to <code>hierarchical Dirichlet Process mixture</code>. But I am having difficulty in understa... | 71,753 |
<p>I have a medical background, with absolutely no knowledge about programming. I am working on survival analysis. I have fitted a multivariate Cox model which I need to cross-validate. My questions are:</p>
<ol>
<li>My dataset is small (79 samples & 37 events). Which is the better method of cross-validation - boo... | 33,389 |
<p>I have a small population of N=137 and a (presumably representative) sample of n=81. The corresponding Finite Population Correction (FPC) factor is FPC=SQRT {(N-n)/(N-1)}= 0.64. Can I apply this correction factor to the estimated standard error of the mean regression slope as follows: (1) SEcor = SE * FPC , (2) tcor... | 33,390 |
<p>In his 1967 paper “A Theorem for Prediction” (<em>Studies in Intelligence</em> 11(4)), Jack Zlotnick discusses how some CIA experiments lead to a “modification” of Bayes' theorem, to account for unreliable evidence. He uses prior and posterior odds $\mathrm{P}$ and $\mathrm{R}$ and a likelihood ratio $\mathrm{L}$ fo... | 33,391 |
<p>I have a homework assignment that is giving me a hard time on the statistics. Lets say you have 3 stocks, all with n expected return (mean) $\mu = 8\%$, a risk (standard deviation) $\sigma = 16\%$ and a correlation coefficient $\rho = 0.3$ between every tow stocks. The homework questions is: <code>If you build a po... | 71,754 |
<p>I ran an experiment that identified lame and non-lame cows every day for 325 days from a pool of 936 cows in one herd. At the same time, I collected data on various variables like milk volume, fat and protein % of the milk, weight of each cow, etc., daily on individual cows. I have read various papers and the one th... | 19,090 |
<p>Suppose there are three cards labeled with values 1, 2, and 3, and two of them are chosen at random (without replacement). Let the random variable $X$ be the value on the first card chosen, and let random variable $Y$ be the value on the second. </p>
<p>I understand that the expected value of the first drawn card, ... | 71,755 |
<p>This is the first time I'm doing research in computer vision, and I'm going to be using OpenCV's cascaded training, for which I'm preparing positive samples for training data.
If anyone's experienced in computer vision, I was just hoping they could take a look and let me know: are these images appropriate for traini... | 71,756 |
<p>I have problems regarding analyzing dummy variable using fixed effects in Stata. I am doing research on impact of climate change in food grain production.</p>
<p>Much previous literature states that panel data use fixed effect regarding this types of analysis, as others I also follow the same things <em>but I have ... | 71,757 |
<p>I am a bit new to analytics. I have this survey dataset with the attributes below.</p>
<p>Independent variable:</p>
<ul>
<li>a. Are we trustworthy? (Value: 1 to 10) </li>
<li>b. Do we offer solutions that you need (Value: 1 to 10) </li>
<li>c. Are we proactive (Value: 1 to 10) </li>
<li>d. Do we provides consisten... | 71,758 |
<p>I still remember the Annals of Statistics paper on Boosting by Friedman-Hastie-Tibshirani, and the comments on that same issues by other authors (including Freund and Schapire). At that time, clearly Boosting was viewed as a breakthrough in many respects: computationally feasible, an ensemble method, with excellent ... | 44,352 |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/15285/r2-ess-tss-how-well-my-model-predicts-outcome">R^2, ESS, TSS - how well my model predicts outcome</a> </p>
</blockquote>
<p>I have already posted <a href="http://stats.stackexchange.com/questions/152... | 49,882 |
<p>A general question I'd like to ask. I have two systems, one has complete data, the other one we found only has 80% of data, the rest 20% is missing for reasons yet to be found. But for short term, I still want to work on those 80% of data for analysis, data mining or whatever. But first I want to figure out if missi... | 12,950 |
<p>I have the data:</p>
<pre><code>numbers <- c(0.176, 0.005, 0.022, 0.016, 0.036, 0.095, 0.069 )
Inds <- as.factor(c("P06", "P07", "P08", "P09", "P10", "P12", "P13") )
</code></pre>
<p>and am trying to test for differences in <code>numbers</code> as a function of <code>Inds</code>. The numbers are proportions... | 33,397 |
<p>I am trying to study various factors that result in a single outcome. For example, if we look around factors that results in the stimuli reaction of a person, let's say the heart beat, the blood pressure, temp, and other factors that result in the stimuli reaction of a person, and what if there is any aletration in ... | 33,398 |
<p>Two friends, A and B, are tossing a fair coin together. Each of the first three coin tosses yields a "head", and they're about to toss it for a fourth time. A says the probability that the next coin toss yields a head is $0.5$. B says that since the probability that four consecutive coin tosses all turn up heads is ... | 71,759 |
<p>In a questionnaire study, we asked respondents to express their attitudes towards how different winter climate factors such as snow, slipperiness might affect their choice to walk and cycle to work. The sample composed of 500 individuals and answers were in form of 5 scales rating form very negative to very positive... | 37,731 |
<p>I'm in need a reference card to help in deciding which statistical test to use depending on study design, variance, class size, groups, etc. Anything like this available? </p> | 33,401 |
<p>I'm attempting to fit a relatively straightforward linear model in R, but am in doubt as to whether by-item effects should be included in the model. Any input would be most appreciated!</p>
<p>Study design:
18 subjects edited the same 41 draft translations (sentences), resulting in 738 (18 x 41) different final edi... | 71,760 |
<p>I understand that pattern mining is finding frequent patterns in a given dataset. So, practically it is unsupervised learning. But what is discriminative pattern mining? Does it concern two (or more) labeled sets as in supervised learning? Please explain the difference. </p> | 98 |
<p>Is the package fpp (or any of its previous incarnations like forecast) supported in Ubuntu 12.04 using AWS? It is the only package that R downloads but when you load the library it throws an error. </p>
<p>Here is the error</p>
<pre><code>Error in library(forecast) : there is no package called ‘forecast’
</code></... | 33,405 |
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