question stringlengths 37 38.8k | group_id int64 0 74.5k |
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<p>In a paper I was reading recently I came across the following bit in their data analysis section: </p>
<blockquote>
<p>The data table was then split into tissues and cell lines, and the two subtables were separately median polished (the rows and columns were iteratively adjusted to have median 0) before being rej... | 42,674 |
<p>I am trying to estimate the precision $\tau$ of a normal distribution with either WinBUGS or OpenBUGS:</p>
<p>$c \sim \text{normal}(\mu,\tau)$</p>
<p>$\mu \rightarrow \lambda \cdot t^{-\beta}$</p>
<p>$\tau \sim \text{gamma}(0.1,0.001)$</p>
<p>I tried using a standard approach here by setting $\tau\sim \text{gamm... | 32,016 |
<p>I do know that inverse gamma is a conjugate prior for univariate normal distribution. I guess it's also a conjugate prior for multivariate normal distribution. I'm trying to get the closed-form posterior from an inverse gamma prior and a likelihood based on a multivariate normal distribution expecting to get inverse... | 32,017 |
<p>1) You fit a multiple regression to examine the effect of a particular variable a worker in another department is interested in. The variable comes back insignificant, but your co-worker says that this is impossible as it is known to have an effect. What would you do?</p>
<p>2) You have 1000 variables and 100 obser... | 70,851 |
<p>I was computing partial eta squared for an ANOVA. I can only find a categorization for eta squared which are either 0.02 (small), 0.13 (medium), 0.26 (large) or .001 (small), .06 (medium) or .12 (large). Which categorization is correct/state of the art and do the same values apply for partial eta squared?
Thank you!... | 510 |
<p>Simple question but I can't find the answer anywhere online or in any of my texts. I think people assume you know, but I don't. What is an error structure, specifically for selecting the family distribution for a Generalized Linear Mixed Model? Is it the same as the distribution of your dependent variable?</p> | 32,018 |
<p>Appology if it is rather long. But i'm confused!
What assumptions do i need in order to answer this question?
With having two segments in the population that you wish to compare with respect to their mean scores on the likert-scale questions:</p>
<p>A two-tailed independent samples t-test is to be applied in order... | 70,852 |
<p>I recently read a discussion about ARIMA models where someone said (referring to <strong>d</strong> as in ARIMA (p, d, q)):</p>
<blockquote>
<p>Its true that d=1 takes out deterministic trends when they are present
(they would appear only in the drift term.) But it does more than
that.</p>
</blockquote>
<p>I... | 42,680 |
<p>I have data on tariff rates and a proxy for tariff evasion (that is common in the literature). The data spans a couple of years before the country I'm studying implements a tariff reform and lowers its tariffs. The data also spans many years after the implementation of this tariff reform. Now I'm looking for a suita... | 42,681 |
<p>I have two datasets, A and B, of weighted (x,y) pairs. I computed the best fit lines, L_A and L_B, respectively, of these datasets, and then computed the intersection of these two lines, (x*,y*).</p>
<p>Now, A and B are drawn from random distributions (of the form y=mx+b+e, where e is a normally distributed error t... | 70,853 |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/10234/meaning-of-probability-notations-pzd-w-and-pzd-w">Meaning of probability notations $P(z;d,w)$ and $P(z|d,w)$</a> </p>
</blockquote>
<p>Can you tell me the difference between $p(x \mid \theta)$ and ... | 49,858 |
<p>I am conducting a 2x2 within-subjects design. When I plot my results it appears that there will be an interaction between my variables but unfortunately none is emerging p=0.08. I find it a shame that I can't explore this further with simple main effects. Does anyone have any suggestions?</p> | 32,022 |
<p>We have a pure birth process and want to know the transition distribution by looking at the wait times. My professor wrote: </p>
<p>$$Pr(W_k < t < W_{k+1}) = Pr(W_k \le t) - Pr(W_{k+1} \le t) $$</p>
<p>where $W_k$ is the wait time to $k^\text{th}$ event. </p>
<p>I do not understand how the equality is true... | 70,854 |
<p>Have you ever heard about Child-Pugh cirrhosis score? There are five features, each feature is discretized in three intervals. For each interval you get a point, eg 1 for the first, 2 for the second etc. After computing all points you sum them up and then you get a cirrhosis stages ranked from A to C. Each stage is ... | 32,025 |
<p>I have a question concerning the evaluation of mixture models. Is there a gold standard to compute the goodness of a fit for a mixture model? </p>
<p>What I am concerned about is how one would evaluate if one, two or three gaussians fit a given distribution better. Truly, one could visually inspect that but I am lo... | 70,855 |
<p>Besides obvious classifier characteristics like</p>
<ul>
<li>computational cost,</li>
<li>expected data types of features/labels and</li>
<li>suitability for certain sizes and dimensions of data sets,</li>
</ul>
<p>what are the top five (or 10, 20?) classifiers to try first on a new data set <em>one does not know ... | 32,029 |
<p>I am constructing Cox models that predict survival in a clinical trials cohort. </p>
<p>After speaking to our statistician (who is away at the moment, hence this post), I was advised to take a forward likelihood ratio-test approach to building Cox survival models, starting with a base model and adding the term that... | 32,030 |
<p>Does the magnitudes of principal eigenvectors obtained by PCA have anything to do with correlations of original variables, and can we use PCA for clustering?
Thanks!</p> | 70,856 |
<p>I have a daily sales data for a product which is highly seasonal. I want to capture the seasonality in the regression model. How I can do it? I have read that if you have quarterly or monthly data, in that case you can create 3 and 11 dummy variables respectively . But how to deal with daily data. I would appreciate... | 70,857 |
<p>I have a very beginner question. I am attempting to forecast total 2014 unit sales of a large number of products. </p>
<p>The data I have has 10 points for each individual product, which are the total unit sales for each of the previous 10 years. I also have the total yearly store revenue for the last ten years, wh... | 70,858 |
<p>I recorded a set of experimental rates $r = r(c,T,P)$ at 2 values of $c$ and >15 values of $T$.<br>
$r(c,T,P)$ obeys the following functional form:</p>
<p>$$
r(c,T,P) = \frac{c+1}{1+e^{\frac{W-X*T}{T}}}e^{-\frac{Y-Z*T}{T}}.
$$</p>
<p>Now I am trying to obtain the the 4 parameters $P=\{W,X,Y,Z\}$ via global non-lin... | 70,859 |
<p>Is there anyway to give weights to a gamma regression so that the variance is allowed to be different, dependent on a particular parameter(in this case sampling event)?</p>
<p>When I try to run my code :</p>
<pre><code>Nm5<-glm(myformula,family=Gamma,data=master_mr,weights=varIdent(form=~1| fevent))
</code></pr... | 6,830 |
<p>I run bivariate Granger-causality regressions. Let $y_{t}$ and $x_{t}$ be stationary time series. I test if $x_{t}$ can forecast $y_{t}$ with the following regression:</p>
<p>$$y_{t+1} = \alpha + \beta_{1}y_{t} + \beta_{2}x_{t} + \varepsilon_{t+1}$$</p>
<p>I find that $\beta_{2}$ is significantly larger than zero,... | 70,860 |
<p>I have the following model:
$Y_i = B_0 + B_1X_{1i} + B_2X_{2i} + u_i$.</p>
<p>I want to compute the OLS estimator using $(X'X)^{-1}(X'Y)$</p>
<p>I'm free to choose values for X but Y cannot have concrete values?</p>
<p>Should I be leaving my OLS estimator in terms of Y?
What would be your recommendation?</p> | 32,033 |
<p>I've got a regression model and I've got 12 observations. So, I could and I did create the matrix. I also calculated the OLS estimator. But my professor's question is to find X and Y. I'm new to stats and what is don't understand is that if the value of X and Y have already been provided through table what is it tha... | 70,861 |
<p>I'm wondering whether there are any statistical properties that should differentiate count data and parametric data. In other words, is there an aspect of my data that I can analyze, or a test I can run, that will allow me to determine whether the data is parametric or nonparametric?</p>
<p>My specific research in... | 70,862 |
<p>I have a distribution that can be written as follows:</p>
<p>$$
q(w, \lambda, \phi) = q(w) \times q(\lambda) \times q(\phi)
$$</p>
<p>Here the $q$'s denote densities. $q(w)$ is a multivariate normal distribution of n-dimensions and $q(\lambda)$ and $q(\phi)$ are univariate normal distributions. So, the joint distr... | 32,034 |
<p>I've dived into the field of neural networks and I became enthralled with them. </p>
<p>I have finally developed an application framework for testing trade systems in stock exchanges and now I'm going to implement my first neural network in it.
Very simple and primitive one, not intended for real trading, just for... | 70,863 |
<p>I would like to find out if the sample mean $T^{-1}\sum\limits_{t=1}^T{y_t}$ of the simple random walk $y_t=y_{t-1}+u_t$ with $u_t \sim i.i.d$ $N(0,1)$ diverges or converges? I am looking for a straightforward technical proof.</p>
<p>Theoretically it should diverge as $T$ is less than the claimed rate of convergenc... | 32,036 |
<p>I have been given two formulas:</p>
<p>$$
\hat{\sigma}^2 = \frac{1}{n-p} (Y - X \beta)^T(Y - X\beta)
$$
$$
= \frac{1}{n-p} \sum ( y_i - \hat{\beta_0} - \hat{\beta_1}x_i)^2
$$</p>
<p>I also have</p>
<p>$$
\hat{\mathrm{MSE}} = \hat{\sigma^2}\left(1 + \frac{1}{n} + \frac{(x^* - \bar{x})^2}{\sum(x_i - \bar{x})}\right... | 70,864 |
<p>I have used the <code>orddom</code> package in R with the argument <code>paired = TRUE</code> to calculate the Cliff’s delta for paired groups, and a 4-column-matrix containing 29 rows with values was returned. The ordinal statistics can be retrieved from the first three columns. But comparing 2 paired groups I need... | 70,865 |
<p>Is there a regression estimation methodology that can estimate the following:</p>
<p>$$Y_t = \alpha + \beta X_t^x + \gamma Z_t^z + \epsilon_t$$</p>
<p>where $x,z\in \mathbb{R}$, are freely varying and are chosen by the estimator according to some statistical criteria. </p>
<p>If such an estimator exists why have ... | 32,038 |
<p>I analyzed my data by using maximum likelihood estimation and a Bayesian approach. Now, I want to see which model has a better fit. How could I do this using either plots or numbers? Please be specific if possible.</p> | 40,672 |
<p>I have 3 groups with a distribution of samples. I used ANOVA to compare means of these groups and also fetched mean, SD and SEM.</p>
<p>I have SD and SEM that varies among groups. How can I compare them so that I can say that a group has significative bigger variance than the others?</p>
<p>Simply ordering the SD ... | 70,866 |
<p>Is there an easy way to apply the trend line formula from a chart to any given X value in Excel?</p>
<p>For example, I want to get the Y value for a given X = $2,006.00. I've already taken the formula and retyped it out be:</p>
<pre><code>=-0.000000000008*X^3 - 0.00000001*X^2 + 0.0003*X - 0.0029
</code></pre>
<p>... | 70,867 |
<p>I am new to this site and quite a novice at building causal models with time series data. For the last month, I have been working intensely to build a series of auto.arima models in r that take exogenous regressors. Namely, day of the week indicators, month of the year indicators. The model also includes a continuou... | 70,868 |
<p>I have a dataset, for example, of success factors (columns) noted by several subjects (rows). Basically, when a subject notes a factor, its marked as a yes or no. </p>
<p>I want to do an analysis to find factors that seem to be related or appear together. correlation analysis. I'm thinking of giving the yes/no valu... | 70,869 |
<p>After the very satisfying answer to:
<a href="http://stats.stackexchange.com/questions/69785/how-to-do-regression-with-known-correlations-among-the-errors">How to do regression with known correlations among the errors?</a>
I take the question to my next point of interest:</p>
<p>What can you do when you have a regr... | 32,052 |
<p>Perhaps a naive question here. Is there a local kernel-based approach that is appropriate for modeling rate data of the form y/z, in which y can be 0 but z never is? Omitting z and measuring the mean value of y within a certain bandwidth would introduce bias by ignoring the fact that all observations are not of equa... | 70,870 |
<p>I'm trying to find a way of correcting outliers once I find/detect them in time series data. Some methods, like nnetar in R, give some errors for time series with big/large outliers. I already managed to correct the missing values, but outliers are still damaging my forecasts...</p> | 70,871 |
<p>If I have a normally distributed population of 3.5 million elements, and I want to sample enough of them to make a statement with 99.6% confidence on a 1-tailed test, what should my sample size be? Is 100 enough, or would it need to be significantly larger? </p> | 32,053 |
<p>Can anyone please advise which of the following books I should read:</p>
<ul>
<li><em>Statistics and Data Analysis</em> by Rupert</li>
<li><em>Analysis of financial time series</em> by Tsay.</li>
</ul>
<p>I am interested in applying the theory and mathematics to stock and commodity data. Which one the above books ... | 70,872 |
<p>Let's assume we have a response vector $y$ with "n" observations, and two predictors $X_1$ and $X_2$.</p>
<p>Let's take an example: Let y be the crime rate in 48 states, and $X_1$ = National GDP rate, $X_2$ = National Unemployment rate. Note that the value of $X_1$ and $X_2$ is constant for all the states. </p>
<p... | 32,054 |
<p>I use R. Every day. I think in terms of data.frames, the apply() family of functions, object-oriented programming, vectorization, and ggplot2 geoms/aesthetics. I just started working for an organization that primarily uses SAS. I know there's a book about <a href="http://rads.stackoverflow.com/amzn/click/B001Q3LXNI"... | 70,873 |
<p>I have a situation where I want to perform two tests, where the null hypothesis is rejected if test 1 is significant and test 2 is not significant. If the two tests are independent then I think the power calculation is straightforward:</p>
<pre><code>alpha <- 0.05
ncp1 <- 8
ncp2 <- 0
n <- 100
qval <... | 32,056 |
<p>I've come across a question where I have an MA(1) process like so:</p>
<p>$X_t = b_t - 0.4 b_{t-1}$ (where $b_t$ is a white noise process and $t$ is the time index)</p>
<p>The question asks me to find $\phi_{11}$ (<a href="http://en.wikipedia.org/wiki/Phi" rel="nofollow">Phi</a>) and $\phi_{22}$</p>
<p>From what ... | 70,874 |
<p>For example, if I have gender in the regression formula. My data has 90 Male
and 10 Female.</p>
<p>I know it is not good to have two groups so unbalanced. The estimate of
gender will have relative big standard error. Is there any other downside
for including it as explanatory variable?</p>
<p>What if it is a dep... | 49,437 |
<p>I have a problem, where probability density function is a solution of differential equation. So the usual work would be to solve analytically diff. equations and then obtain samples from that distribution.
However, I started to wonder if it is possible to skip the solving process of equation and directly obtain samp... | 24,410 |
<p>I'm aware of the simple 'proof' that shows random walks with a normal error term are non-stationary in original form and stationary in first-difference form but what happens if the errors have a different distribution?
I'm looking into modelling these errors under different distributions, but am concerned that if I ... | 32,059 |
<p>From the Wikipedia page on <a href="http://en.wikipedia.org/wiki/Confidence_interval">confidence intervals</a>:</p>
<blockquote>
<p>...if confidence intervals are constructed across many separate data analyses of repeated (and possibly different) experiments, the proportion of such intervals that contain the true... | 70,875 |
<p>Full disclosure: this is a homework problem. I'm having a really hard time understanding the algorithm for applying SIS to contingency tables or what it even means to do sequential importance sampling in this case. </p>
<p><img src="http://i.stack.imgur.com/6iztV.png" alt="enter image description here"></p>
<p>So ... | 32,060 |
<p>This is unconstrained optimization. First Order Necessary Condition (FONC) gives me two equations that are contradicting each other. x1 + x2 = 5 and x1 + x2 = -5. What does this imply?</p> | 32,061 |
<p>I would like to know why some languages like R has both NA and NaN. What are the differences or are they equally the same? Is it really needed to have NA?</p> | 32,064 |
<p>Measurement outcome is a continuous number measured in $p$ locations.
This yields a vector $X_1$ to $X_p$ per subject. These vectors are obtained on $N$ subjects.
In addition these $N$ subjects come from $k$ groups.</p>
<p>What method should I use to compare the average vector across the entire study population to ... | 32,065 |
<p>I have analyzed an experiment with a repeated measures ANOVA. The ANOVA is a 3x2x2x2x3 with 2 between-subject factors and 3 within (N = 189). Error rate is the dependent variable. The distribution of error rates has a skew of 3.64 and a kurtosis of 15.75. The skew and kurtosis are the result of 90% of the error rate... | 70,876 |
<p>I am using Kullback–Leibler divergence criteria for comparing my estimation and true density functions, but I have zero value on my estimation function when I have a testing set of size 10000, mostly in the last testing points. Finally, I get infinity because of the formula of KL as follow,</p>
<p>$$ KL = \int_R f(... | 70,877 |
<p>I was wondering if anyone had experience with SAS/IML and R, and can give some pointers as to the relative advantages/disadvantages of the two. I've used R extensively for programming and statistical analyses, but haven't had much experience with IML. However, as this company is a SAS shop, I'm likely to have to use... | 32,066 |
<p>I'm new to data analysis so this is kind of a simple question.</p>
<p>I would like to understand why I cannot reproduce a survival curve generated by a fitted exponential model from Stata. I use the coefficients and make my function in R to plot but it looks nothing similar. I believe it's one of those daft problem... | 70,878 |
<p>I am looking to How do you solve for the optimum values with the lowest MSE for the coefficients and dampening constant in exponential smoothing and ARIMA models? What are the equation used?</p> | 32,071 |
<p>I'm trying to understand the built of a random forest with the $10\times10$ cross
validation for a binary classification problem. Therefore I have 4 basic
questions:</p>
<p>Notation:</p>
<ul>
<li>$N=500$ trees</li>
<li>$i=$ index for a tree</li>
<li>$mtry=$ Number of variables randomly sampled as candidates at e... | 70,879 |
<p>Following experimental design was done and some data as shown in table below was obtained:</p>
<p>pretest> intervention1> intervention2> posttest > perception survey</p>
<p>Number of students=60</p>
<p>Number of Students subjected to intervention=20</p>
<p>Independant variable is "Intervention2" which possible i... | 70,880 |
<p>I have some software that calculates a lot of probabilities. I thought it would be interesting to look at what happens with my simulation if I increase each probably by a factor of 'x'. So far I've looked at x ranging from 2 to 25 and the results are somewhat as expected. My question is what am I actually simulating... | 32,072 |
<p>Consider $X_n = \begin{cases} 1 & w.p (1 - 2^{-n})/2\\ -1 &w.p~ (1 - 2^{-n})/2\\ 2^{k} &w.p~ 2^{-k} \text{ for } k > n\\ \end{cases}$</p>
<p>I need to show that even though this has infinite moments, $$\sqrt{n}(\bar{X}_n) \overset{d}{\to} N(0,1) $$</p>
<p>I have tried showing this by using Levy's ... | 70,881 |
<p>(I'm assuming the second $\bar x$ should be a $\bar y$), but I'm mostly confused how to solve this problem because it seems like since $\bar x$ and $\bar y$ are values, not random variables, $W$ is just a value? If that's the case, how can you take the expected value and variance of $W$? Thanks.</p>
<p><img src="... | 70,882 |
<p>I am starting a work on electric vehicle to see how the charging process can impact the local electricity network. I would like to know if there exists public data of driving "habits". </p>
<p>Ideally, I would like time series data for bigh fleets of vehicles in a relatively big city. For a given car these data cou... | 32,074 |
<p>I am looking to cluster thousands of emails in one's mailbox. Different from traditional analysis with emphasis on email body, the attachments will play a big role in my work. </p>
<p>The data set contains email with attachment and those without attachment, and the features will be extracted from two parts:</p>
<o... | 70,883 |
<p>I was going through the <a href="http://fidoalliance.org/about/faq/" rel="nofollow">FAQ page</a> of the <a href="http://fidoalliance.org/" rel="nofollow">FIDO alliance</a>, a consortium to implement a next generation authentication system. To answer to the question,</p>
<blockquote>
<p>How secure are fingerprints... | 32,075 |
<p>$A$, $B$, $C$, $D$ are positive integers.</p>
<p>$$A \sim Binomial(p_1, A+B)$$</p>
<p>$$A+C \sim Binomial(p_2, A+B+C+D)$$</p>
<p>My variable of interest is $p_1/p_2$</p>
<p>Could one analytically compute a distribution (preferably exact) for this variable? What would be its mean and variance (how to compute it?)... | 32,076 |
<h2>Disclaimer</h2>
<p>I am new to this site, relatively new to R (two weeks of learning), have just a really basic knowledge in statistics so sorry if I'm doing a dumb mistake there or asking bad question or something.</p>
<p>I also don't know how to nicely embed my dataset into post (I searched meta without finding... | 70,884 |
<p>I am doing Cox regression models and KM plots for a data set where the end point is death. In addition there is information about whether the death was cancer-specific or not. So I have three categories:</p>
<ol>
<li>No death, last seen is the date of censor</li>
<li>Death - cancer-specific</li>
<li>Death - other... | 70,885 |
<p>I have a web-site, and I found the distribution of user number in a day have an obvious pattern. Not only my own site, I see almost all usage distributions of web-site fit model like this. They look like sine wave. I would like to use the model to predict how many total bandwidth I will use if I know the peak of usa... | 70,886 |
<p>Assume that $w$ follows a lognormal distribution $f(x)$. Given $a>0$, can the function:
$$
\int_ {x_0}^\infty \log(1+a\cdot x)\cdot f(x)\cdot dx
$$
be written in a closed form? </p> | 70,887 |
<p>I have a quick question:</p>
<p>In using a t.test for multiple experiments, I got one p-value for each experiment.<br>
When I plot the histogram of these p-values, I find the distribution looks like a bell-shaped curve, i.e. majority is centered around 0.5 to 0.8, very few > 0.9, but there are some < 0.05. </p>
... | 70,888 |
<p>From <a href="http://en.wikipedia.org/wiki/Portmanteau_test" rel="nofollow">Wikipedia</a></p>
<blockquote>
<p>A portmanteau test is a type of statistical hypothesis test in which the null hypothesis is well specified, but <strong>the alternative hypothesis is more loosely specified</strong>. Tests constructed in ... | 70,889 |
<p>I've been playing around a little with basic probability and I was wondering if there is any intuitive meaning to either,</p>
<p>$$
P(A|B)P(B|C) \quad\text{or}\quad \sum_{B} P(A|B)P(B|C).
$$</p>
<p>After playing with the definitions I didn't see any obvious simplifications, but I feel there should be one. I though... | 32,081 |
<p>In soccer (or any discipline with similar scoring rules), is there statistically equal chance for win, loss and tie?</p>
<p>So, there are 3 possible outcomes, but are all 3 outcomes equally possible?</p>
<p>This does not take into account better/worse teams, so teams are equal for the chances... So ranking, player... | 70,890 |
<p><img src="http://i.stack.imgur.com/0J1bC.png" alt="The snippet from the book is pasted below. I don't understand how the denominator is not a function of theta as it is integrated over theta"></p>
<p>The snippet from the book is pasted above. I don't understand how the denominator is not a function of theta as it i... | 70,891 |
<p>I want to apply the Machine learning to a problem which has 9000 input rows in 132 predictive variables but outputs only for 28 of them. Should I be better of using unsupervised learning methods?. Actually the inputs are continuous while output is taken once every day.</p> | 70,892 |
<p>Please note that I am asking for advice regarding general approaches to analysis in this question.</p>
<p>I have a time series of some $p$ variables and $n$ observations (going back several years and with resolution of approximately 15 minutes). The variables are the numbers of product $p_i$ sold, and each sale ha... | 70,893 |
<p>When using a pre-test/post-test assessment to measure college learning, what is a meaningful significance level? I realize that p<.05 is the minimum criterion, yet with a correlated-groups t-test, it doesn't take much improvement to achieve this significance level. I'm getting p<.0001 by achieving only a mod... | 32,083 |
<p>I'm doing some software testing where we are measuring specific latencies. Generally we run the same test several times to just eyeball the results and make sure that they are consistent across runs. I usually do this by plotting the cumulative distributions for each run together on a graph, and look for an anomal... | 5,366 |
<p>We performed a randomized controlled trial. I am interested in anxiety levels (dependent), treatment (meds vs. ultra-dance therapy), and personality variables (agreeableness, neuroticism, weeaboo). We measured anxiety levels four times. I am interested in exploring whether participants in one treatment experienced g... | 32,084 |
<p>Consider a case where instead of observing actual variable values, we are observing variable range. The possible range-values could be enumerated (i.e. could be a fixed set of values, for e.g. fixed age-group ranges) or could be observation specific (and might overlap). </p>
<p><s>In the former case, the variable c... | 70,894 |
<p>This probably seems like a really strange question, but let me try to explain what I want to do; hopefully it will make sense.</p>
<p>I have a data set with a couple dozen variables, such as age, level of education, self-assessed (via a Likert scale) measures of technical ability, experience, willingness to share p... | 70,895 |
<p>I am reading <a href="http://ilpubs.stanford.edu:8090/508/1/2001-41.pdf" rel="nofollow">SimRank</a> paper by Jeh and Widom which tries to find the similarity between objects based on the relationships between them. Effectively, SimRank is a measure that says "<strong>two objects are similar if they are related to si... | 5,382 |
<p>I'm looking to implement a coordinate descent solution to the Elastic Net (Friedman et al, 'Regularization paths for generalized linear models via coordinate descent') for logistic regression. The paper explicitly gives the coordinate update for the linear case, but I'm having difficulty understanding the solution ... | 32,089 |
<p>I have done an experiment in which I have measured the energy required to chew three different food samples on 10 subjects with 3 repetitions per sample. I am interested therefore in finding out whether there is a difference between samples according to the energy consumed.</p>
<p>I have performed a Friedman test b... | 70,896 |
<p>I have met two k-fold cross-validation strategy. Both method divides the data set to k-folds, say k = 10. First one chooses the validation set elements randomly while the second one chooses incrementally. Let me explain this with an example:</p>
<p>Method 1 chooses 3 random folds in order to use as validation set a... | 70,897 |
<p>I would like to ask for your help with the following issue. I am trying to estimate the model where dependent variable is a share of total (e.g. share of the US economy in terms of GDP on total world GDP). I use the panel data for 27 cross sections (countries) and 8 time dimensions (years). By definition, for each y... | 70,898 |
<p>I am looking for studies that compare different spatial interpolation methods for observed data. However I am looking for studies that have also compared observed with generated synthetic data.</p>
<p>For example, the comparison of spatial interpolation methods using both the data obtained from a couple of stations... | 15,130 |
<p>My client wants me to implement Variable selection methods i.e. Forward, Backward, Step and LASSO in VB .Net platform including p-value and AIC. I have no idea about the steps involved to calculate above variable selection method. Can anyone tell me each steps including sub-steps calculation or formula. Also I am un... | 70,899 |
<p>In general I'm wondering if there's any danger in studying from older edition statistics books. The undergrad material seems to have remained unchanged throughout the last century, but I'm looking for 'the next step', which makes me wonder if older editions will be modern enough.</p>
<p>For example, Applied Multiva... | 70,900 |
<p>The R code "intervals()" gives confidence intervals for fixed effects only in a mixed model.</p>
<p>*Is there a reason why only fixed effects' confidence intervals are provided?</p>
<p>*Is there any way to get confidence intervals for random effects as well?</p> | 5,396 |
<p>Given I understand why PCA aims to maximize variance, I wonder why finding non-gaussian projections is interesting for Projection Pursuit, i.e., what is the motivation of this reasoning?</p> | 27,571 |
<p>I have frequency data for 9 populations, divided into two groups, one of five populations and one of four. I am interested in whether these two groups are different. </p>
<p>A classic way to analyse such data, I think, is a CMH test where, in my example, I could construct a 2 x 2 x k test, where k is 4 = number o... | 70,901 |
<p>Assume a general linear model $y = X \beta + \epsilon$ with observations in an $n$-vector $y$, a $(n \times p)$-design matrix $X$ of rank $p$ for $p$ parameters in a $p$-vector $\beta$. A general linear hypothesis (GLH) about $q$ of these parameters ($q < p$) can be written as $\psi = C \beta$, where $C$ is a $(q... | 42,773 |
<p>Consider $n$ independent uniform random variables $X_i \sim U(-\theta,\theta)$, and
let $Y_1 = \min(X_1, \ldots, X_n)$ and $Y_n = \max(X_1, \ldots, X_n)$ . </p>
<p>What is distribution of $Z = \max (-Y_1,Y_n)$, given that the joint PDF of $Y_1$ and $Y_n$ is
$$
f(y_1, y_n) = \frac{n(n-1)}{(2θ)^n} (y_n-y_1)^{n-2} , ... | 32,096 |
<p>I applied two different classifiers against the same validation set. It turns out that classifier A is better than classifier B in terms of ROC curve. However, classifier B is better than classifier A in terms of confusion matrix. How to explain this kind of contradiction?</p> | 32,097 |
<p>I have some associated categorical dependent variables that are ordinal in nature (with 4 or 5 categories). If I want to see the effect of a set of independent variables (which can be both continuous and categorical) what is the right way to perform the regression? </p>
<p>Should that be a multivariate generalized ... | 49,782 |
<p>Given a distribution $\{p(X|\theta),\theta\in\Theta\}$:</p>
<ul>
<li><p>how do you show the existence/non-existence of its conjugate prior?</p></li>
<li><p>what are some general ways/principles to construct/find its conjugate prior, if there is one? </p></li>
<li><p>If it exists, how do you show it is unique or not... | 70,902 |
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