question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>Given are $Z_1, Z_2$ i.i.d. standard normal.</p>
<p>Find</p>
<p>$P[Z_1 < t < Z_2]$</p>
<p>I have difficulties with working out how I should split the condition.</p>
<p>Is $P[Z_1 < t < Z_2] = P[Z_1 < t, t < Z_2]$ or is some additional condition required?</p>
<h2>My question</h2>
<p>How should ... | 74,289 |
<p>I found an example for manually calculating the hazard ratio when there are two groups.</p>
<pre><code>d2 <- c(2, 2, 1, 2, 2, 0, 0, 4, 0, 2, 2, 0, 1, 0, 1, 1, 1)
d <- c(2, 2, 1, 2, 2, 3, 1, 4, 1, 2, 2, 1, 1, 1, 1, 2, 2)
r2 <- c(21, 19, 17, 16, 14, 12, 12, 12, 8, 8, 6, 4, 4, 3, 3, 2, 1)
r1 <- c(21, 21, 2... | 74,290 |
<p>I am reading a code for a Bayesian clustering method. Both prior and the likelihood are normally distributed. If I understood correctly, such cases are called "conjugate priors"</p>
<p>My question is about calculating the posterior mean and variance. So it is implemented in the code as following</p>
<pre><code>d =... | 74,291 |
<p>I am plotting a density estimate for misclassification rate of some classifier using the standard <code>plot</code> and <code>lines</code> functions. Even though I've set <code>xlim=c(0.32,0.38)</code> and <code>ylim=c(0,100)</code> within the <code>plot</code> command, the x-limits and the y-limits are a bit wider ... | 74,292 |
<p>The structural form of the linear simultaneous equations model <a href="http://en.wikipedia.org/wiki/Simultaneous_equations_model" rel="nofollow">simultaneous equations model</a> can
be written as</p>
<p>$
\mathbf{y}_{i}^{\prime}\Gamma+\mathbf{x}_{i}^{\prime}\mathbf{B}=\epsilon_{i}^{\prime}
$</p>
<p>which can be... | 1,034 |
<p>I know there are methods to calculate a confidence interval for a proportion to keep the limits within (0, 1), however a quick Google search lead me only to the standard calculation: $\hat{p} \pm 1.96*\sqrt\frac{\hat{p}(1-\hat{p})}{N}$. I also believe there is a way to calculate the exact confidence interval using ... | 39,847 |
<p>Okay I have given this a go but I think it is totally wrong. Can someone please make this correct for me ? To understand the MA(q) model I really need to plug some numbers into it as I', finding these time series formula epically confusing as it is never explained what any of it actually is in the real world.</p>
<... | 31,305 |
<p>I am running a Monte-Carlo simulation and I sample from various normal distributions. I was just wondering, is there a way by which I can increase the probability of selecting a point from the tails (i.e., $[-5\sigma,-3\sigma]$ and $[3\sigma,5\sigma]$) as compared to the probability associated with the interval $(-3... | 74,293 |
<p>I am using logistic regression to predict y given x1 and x2:</p>
<pre><code>z = B0 + B1 * x1 + B2 * x2
y = e^z / (e^z + 1)
</code></pre>
<p>How is logistic regression supposed to handle cases in which my variables have very different scales? Do people ever build logistic regression models with higher-order coeffic... | 74,294 |
<p>An online module I am studying states that one should <strong>never</strong> use Pearson correlation with proportion data. Why not?</p>
<p>Or, if it is sometimes OK or always OK, why?</p> | 74,295 |
<p>I have data from a set of sensors, and would like to measure similarity between two samples of data ignoring local fluctuations.</p>
<p>My problem is, my sensors are not regularly placed : some are quite alone, others are many in the same area, there is no regular pattern in their locations.</p>
<p>I want to measu... | 74,296 |
<p>In <a href="http://surveyanalysis.org/wiki/Multiple_Comparisons_%28Post_Hoc_Testing%29" rel="nofollow">http://surveyanalysis.org/wiki/Multiple_Comparisons_(Post_Hoc_Testing)</a></p>
<p>It states "For example, if we have a p-value of 0.05 and we conclude it is significant the probability of a false discovery is, by ... | 74,297 |
<p>I just used the standard formula to determine the sample size of a sample to match the mean of a pupulation with an error margin of 3 percentage points and with a 90% probability.
I know would like to check that the mean of my sample is actually within the 3% margin of error of the mean in the population.
To do so ... | 49,338 |
<p>I know correlation does not imply causation. I have read it nth time. (i.e. weight does not cause height etc. etc.)</p>
<p>However, to find the effect of a moderator variable on X-Y relationship, a regression model is used such as the GLM in SPSS to test for interaction or multiple regression. See <a href="http://s... | 37,371 |
<p>In <a href="http://books.google.co.uk/books?id=6-Y8OL3sW14C&pg=PA102&lpg=PA102&dq=deviance%20of%20a%20%22bernoulli%22%20model?%20goodness%20of%20fit&source=bl&ots=kb3FoEbN30&sig=gJ28_j0CN8-WsFoYp4gDrL2eooA&hl=en&sa=X&ei=SsFhUe3YL-Wa0QWTo4CwBg&ved=0CDsQ6AEwAQ#v=onepage&q=de... | 74,298 |
<p>I would really appreciate some advice.</p>
<p>I have two sequential measurements of severity of illness $(s_1, s_2)$ that are incompletely observed along with an outcome measure ($y$). I am trying to estimate if the change in the measurement $(d = s_2 - s_1)$ adds anything to a model based on the second measuremen... | 74,299 |
<p>This is a questions I got for homework in <em>test planning and variance analysis</em>. I apologize in advance for the way my professor phrases things :D
I would love to hear hints or tips on how to approach this.
So here goes:</p>
<blockquote>
<p>A statistician decides to perform the next a-parametric test to e... | 37,119 |
<p>In this <a href="http://tamino.wordpress.com/2013/04/06/sampling-rate/" rel="nofollow">blog article</a>
an example is given of one can use the DFT to detect frequencies much higher than the sample rate.
In the comments sections I asked how it was done, since DFT normally requires evenly sampled data. The author of t... | 74,300 |
<p>I feel like every question I've asked on CrossValidated has lead back to looking at the number of observations I have per variable. I understand that there are many rules of thumb out there depending on your field, your expected effect size, etc. These come back to recognizing that too few observations can lead to o... | 37,123 |
<h1>Problem</h1>
<p>I want to estimate the probability of a user choosing a car or transit as a transport mode. Following is the output of the simple logistic regression:</p>
<p><img src="http://i.stack.imgur.com/9qQZC.jpg" alt="enter image description here"></p>
<p>I want to estimate the probability of choosing car... | 74,301 |
<p>Context: I am working on a decision tree classifier, trying to classify businesses as to whether they are likely to have an event occur (default) in the next 90 days.</p>
<p>One input I get is whether, and when, the business is scheduled to have a related event (let's call it "warning"). A business may have no war... | 74,302 |
<p>I am working with matrices, of the size N*M, where each cell corresponds to the Pearson's correlation between two time series. I want to threshold each matrix such that it would retain only significant correlations. Now, my problem is that the time series are very large (>1500 data points) and thus rather weak corre... | 74,303 |
<p>Let's assume we have a training set with $y \in \mathbb{R}$. Thus all the data is between $y_{min}$ and $y_{max}$. If we built a decision tree model it cannot return $y_{pred}$ outside the given range (using any combination of input features). Thus decision tree cannot extrapolate in terms of predicted values. Can a... | 570 |
<p>I was wondering what the following OLS scenario would imply: a variable is endogenous (i.e. correlated with the error term) yet is statistically significant.</p>
<p>Alternatively, what if in, once again OLS, the variable is exogenous yet statistically insignificant (although the overall regression is indeed statist... | 37,130 |
<p>I found several similar questions with no answer. But I'm gonna give it a shot anyway. </p>
<p>I'm trying to find assets (stocks) which are co-integrated, since Engle-Granger's test may give cause to spurious regression it's suggested by several articles that you use Johansen's test as well to ensure a long-term co... | 47,705 |
<p>I've been using igraph and statnet to do most of my network analysis, but I am trying to replicate results that I use MPNet (an expansion to <a href="http://sna.unimelb.edu.au/PNet" rel="nofollow">PNet</a>) in order to perform some simulations on a multi-level network. I'm hoping someone has experience with PNet or ... | 74,304 |
<p>I have a set of data that represents periodic readings. The data shows an upward trend but I need to test for a statistical difference from zero. I believe I should use the t test, two tailed but what should I use for the second set of data? Zeros, the starting value?</p>
<pre><code>0.2245
0.243
0.2312
0.1795
0.192... | 48,875 |
<p>is it possible for an algorithm A to have a better precision but worse recall (or better recall but worse precision) than another algorithm B?</p>
<p>Although I know that precision and recall are different things, it seems to me that if algorithm A has a better precision (or recall) than algorithm B then algorithm ... | 46,203 |
<p>Suppose I have some kind of distribution which gives the probability of observing a given value (assume that this distribution is <strong>not</strong> normal).</p>
<p>Now, I have a certain observation and I want to calculate how likely it is to observe a value that is equally or more extreme under this distribution... | 37,136 |
<p>How can I find the standard deviation in categorical distribution, where the elements have non-numerical attributes (e.g. colors)?</p>
<p>For example, I have a bag of marbles with $n$ colors. There's an infinite number of marbles in the bag, and are biased towards a certain color with a probability of $\frac{x}n, x... | 74,305 |
<p>I have recently interviewed for a statistical analysis job and was asked a question about why linear least squares regression fails when the data is heteroskedastic. The correct answer to this question, according to the interviewers, is that heteroskedastic data means that the equation of the regression line produce... | 37,138 |
<p>I am stuck in understanding how the output of convolution operation is obtained. Can somebody please show the steps? The question is an image is processed by applying 3*3 mean filter . What is the impulse response? </p>
<p>The formula is $g(m,n) = \sum_{\alpha = 0}^{M-1} \sum_{\beta=0}^{N-1} f(\alpha,\beta)h(m-\alp... | 74,306 |
<p>Imagine I have a time series for an animal population and a time series for a climatic variable during the same time period and at the same location. Unfortunately the data are observational (i.e., no experimental manipulation). Now imagine there is a decreasing linear trend in both variables (and no seasonality).<... | 37,141 |
<p>I was wondering if anyone could help me on how to interpret the coefficient from an analysis I have carried out in R (<code>survival</code> package). </p>
<p>The data is right censored, the dependent variable (time to event) was modelled under the gaussian distribution and the independent variable is a categorical ... | 37,142 |
<p>I need some help
My project aims to develop algorithms for spatial temporal analysis of Flickr, Twitter and Foursquare databases to detect any kind of significant changes, named as “Event” in real time. Event can be defined as any anomalous user activity, which happens at a time or within a specific period of time. ... | 49,929 |
<p>I obtained data of typical time point in two conditions in this shape:</p>
<pre><code>weight condition time
0.1307857 Transf 1
0.1926429 Transf 2
0.2734286 Transf 3
0.4403571 Transf 4
0.6037143 Transf 5
0.9036429 Transf 6
1.5454286 Transf 7
0.1370714 Unt 1
0.20... | 74,307 |
<p>I have four samples $x_1, x_2$ and $y_1, y_2$ with $n_{x1} \neq n_{x2} \neq n_{y1} \neq n_{y2} $. I calculated, using a Wilcoxon rank sum test, that $x_1$ is significantly different to $x_2$ and $y_1$ significantly different to $y_2$. </p>
<p>However, I would like to test whether the difference $x_1 - x_2$ differs... | 74,308 |
<p>I perform a permutation test multiple times on different datasets, each time I am only concerned about significant $p$ values. To reduce computation time would it be correct to introduce this kind of stopping rule: After a certain number of $N$ permutations to check whether $p$ is greater than a particular value. So... | 74,309 |
<p>I have read other posts on conducting Factor analysis (FA) with dichotomous variables and although it appears clear that FA done in the default way is not appropriate, I am still unclear about a few things. </p>
<p>I have 7 variables that are yes/no responses. They are assessing peoples functioning (e.g., working y... | 74,310 |
<p>I have a time series data set. I can decompose it and get the trend but I would like to put confidence ranges around the trend (past) not the forecast-ed component. The decompose function also doesn't handle N/As very well so is there another way to define the trend with data that has N/As. I have been trying to ... | 74,311 |
<p>I have a data set and I have to fit this data set with a stable distribution. The problem is that the stable distributions are known analytically only in the form of the characteristic function (Fourier transform). How can I do this?</p> | 74,312 |
<p>I have two sets of data. The one is daily temperature data and another is 16-day vegetation observation data (value of Jan 1, Jan 17 etc), throughout a year. But I need daily values of vegetation observation data. How to obtain daily value from 16-day vegetation data?</p> | 74,313 |
<p>I came across an article where the authors did a Principal Component Analysis on gene expression data, and found out the genes that are most correlated to the 1st principal component, and they used that gene list for further analysis.
Can somebody tell me how to find out entities (genes in this case) that are most c... | 74,314 |
<p>The only thing I understood about fuzzy neurons is that the neuron's activation function is replaced with some operation used in fuzzy. Other than that, I didn't understand much from science paper I found. Also, it is hard to just Google it because of it's name, which results in listing some fuzzy or ANN or hybrid s... | 74,315 |
<p>As title, I have a correlation matrix available with cor() function </p>
<pre><code> corMatrix<-cor(mydata)
corMatrix is a 98 by 98 matrix storing positive and negative correlation values.
</code></pre>
<p>I want to assess which correlations values are significant among all the correlations. Permutation... | 74,316 |
<p>One particular assumption is that $e_{i} \sim N(0,\sigma^{2})$ but I was wondering why we use a QQ plot to test this assumption since we have $n$ iid distributions to look at. When we use a QQ plot, aren't we looking for the normality of all the residuals as opposed to one particular $e_{i}$? I am confused about thi... | 74,317 |
<p>Reposted from Math.SE:</p>
<p>Continuing from <a href="https://math.stackexchange.com/questions/593512/what-is-a-function-satisfying-these-constraints">this question</a>. Given two random variables $X$ and $Y$ where $X \sim \operatorname{Beta}(a, b)$ and $Y \sim \operatorname{Beta}(c, d)$, I'm looking for a random ... | 74,318 |
<p>Here is the data I have:</p>
<ul>
<li>Response variable : It contains proportions and it takes discrete values 0, 0.2, 0.4, 0.6, 0.8, 1. But there are 109 possible discrete values</li>
<li>Predictor variable.1: Discrete and ordinal. It contains these values 10, 20, 30, 40.</li>
<li>Predictor variable.2: Discrete an... | 74,319 |
<p>I am working on a machine learning experiment comparing the use of multiple different neural network classifiers by applying them on a large number of datasets, using stratified 10-fold cross-validation. I measure the performance as the average of the errors on the validation set (sometimes referred to as test set) ... | 6,992 |
<p>I have developed two new sorting techniques using C language. I need to compare the performance of the both sorting techniques, to see which one is better than another. To do this, I used different input data, from n = 500 to n = 2500.
For each data that need to be sorted, I run them 10 times and get the mean, stan... | 37,157 |
<p>I am using a standard version of logistic regression to fit my input variables to binary output variables.</p>
<p>However in my problem, the negative outputs (0s) far outnumber the positive outputs (1s). The ratio is 20:1. So when I train a classifier, it seems that even features that strongly suggest the possibili... | 37,158 |
<ol>
<li><p>If the items to be "summed" or combined to create an overall index are collectively the underlying construct (i.e. I am trying to measure compliance to an intervention which has different components), wouldn't combining all the components for IRT violate the assumption of unidimensionality since they repres... | 74,320 |
<p>My memory is fuzzy on the advantages and disadvantages of various methods for detrending time-series data. I'm looking for a succinct summary of why and when one should or should not use the following:</p>
<ul>
<li>Differenced data</li>
<li>Log-differenced data</li>
<li>Error term, after regressing on <em>only</em>... | 74,321 |
<p>What is the best way of going about dealing with few instances in support vector regression, e.g. only approximately 40? Also - is there an optimal way of dealing with outliers in this case of few instances?</p> | 37,160 |
<p>I have two models - one is including a categorical covariate as a fixed effect, the other includes it as a random effect:</p>
<pre><code>require(nlme)
set.seed(123)
n <- 100
k <- 5
cat <- as.factor(rep(1:k, n))
cat_i <- 1:k # intercept per kategorie
x <- rep(1:n, each = k)
sigma <- 0.2
alpha <-... | 74,322 |
<p>I have always been taught that random effects only influence the variance (error), and that fixed effects only influence the mean. But I have found an example where random effects influence also the mean - the coefficient estimate:</p>
<pre><code>require(nlme)
set.seed(128)
n <- 100
k <- 5
cat <- as.factor... | 74,323 |
<p>I'm analyzing users' in-game data in order to model whether they're going to be paid user or not. </p>
<p>Here's my model:</p>
<pre><code>Logistic Regression Model
lrm(formula = becomePaid ~ x1 + x2 +
x3 + x4 + x5 + x6, data = sn, x = TRUE,
y = TRUE)
Model Likelihood Discrimin... | 74,324 |
<p>I can think of different “types” of multiple testing when using linear models for example:</p>
<ol>
<li>Multiple inferences because we have several dependent variables</li>
<li>Multiple inferences because we have several independent variables</li>
<li>Looking at the data without making any test. Running a test on o... | 37,166 |
<p>I need to proof that $X$ follows a distribution $F$ with probability $1-p$ and a distribution $G$ with probability $p$ if, and only if, its distribution function is:</p>
<p>$(1-p)F + pG$</p>
<p>Can anyone give me some hints about how to proof this?</p>
<p><strong>EDIT2</strong>: this is my <em>second</em> take ba... | 74,325 |
<p>In statistics people gather a lot of data (ie heights of people or gene expression levels) to get some insight. Then in order to perform statistical analyses they try to fit their data to a theoretical distribution (ie Normal Distribution) by computing some parameters.</p>
<p>How do we know that our data follows su... | 74,326 |
<p>I have a 5 x 2 design where one of the levels of the first factor is a control, all others are experimental conditions. I'm interested in the interaction between the two factors and especially, if the interaction is present for each of the 4 experimental conditions with the control condition.</p>
<p>I conduct 4 sep... | 74,327 |
<p>The company where I work did a survey with a complex sample. Originally, the sample was a 2-step stratified, but due to some problems, we lost one of them (so, let's consider that the sample is stratified only on 1 variable).</p>
<p>The biggest part of the questions is like "What you think the company can do in res... | 74,328 |
<p>I have data that involves 2 groups (equal sample size in each) and data for each group over 3 time points (they are actually 3 different monetary reward conditions). I want to investigate within group differences. All time/condition points are important, I don't have a "control" time point.</p>
<p>Any opinions on t... | 48,906 |
<p>I am trying to determine why people ask if a model of a health care risk (for inpatient stay, or acquiring a disease or any outcome) is a population risk model or an individual risk model. This is in a clinical setting where the outcome is some medical event and covariates are personal health history and demographic... | 37,174 |
<p>Following cardiac surgery, patients are encouraged to exercise regularly (assume that regular exercise is defined as exercising on 3 or more days per week). A physician suspects that patients exercise regularly immediately following cardiac surgery but tend to reduce, even stop exercising completely, over time. An i... | 37,175 |
<p>First, I need to prove that the distribution of a RV X, where X|lambda ~ Pois(lambda), and lambda ~ gamma(a, B), is a negative binomial. I know that it <em>is</em>, but why negative binomial instead of another 2 parameter distribution? How do I prove negative binomial is the best alternative in the circumstance of a... | 74,329 |
<p>How can I interpret McLeod-Li test results below</p>
<pre><code>> McLeod.Li.test(y = data, gof.lag = 12, plot = FALSE)$p.values
[1] 7.602866e-09 0.000000e+00 0.000000e+00 0.000000e+00 0.000000e+00 0.000000e+00
[7] 0.000000e+00 0.000000e+00 0.000000e+00 0.000000e+00 0.000000e+00 0.000000e+00
</code></pre>
<p>... | 74,330 |
<p>I have a list of objects and their frequencies of occurrence in R</p>
<pre><code> Names <- c("a","b","c","d","e")
Freq <- c(12,45,67,100,1 ...)
</code></pre>
<p>I want to rank the prominence of these objects based on the frequency. Is there a way to fit a distribution on the frequencies and weight the... | 74,331 |
<p>What is the difference between </p>
<p>$ \lim_{n \to \infty} \ \mathrm{E}_{\theta}(T_n(X)) = \theta$ </p>
<p>and </p>
<p>$ T_n(X) \xrightarrow{p} \theta \ $ for $\ n \xrightarrow{} \infty$ ?</p>
<p>(unbiasdness vs. Consisteny)</p>
<hr>
<p>Ups... there seems to be this question already :-(
<a href="http://... | 49,379 |
<p>I have been trying to estimate the MLE for my joint posterior. I'm using R and the package stats4. I have 14 parameters and two of them are $\geq 0$, which I did not know how to implement (and I was creating NaN due to the minus log posterior required in for the mle function) and I just made it return very high valu... | 74,332 |
<p>Recently I attended a workshop on probability, I was asked the following question but I did not find a way to solve it. A discussion on this question can help to learn something new.</p>
<p>We were told that, We are guests in a game show and close to win a great fortune. The quiz master asks us to choose one of thr... | 49,611 |
<p>Let $X_1, X_2, ..., X_n$ be a random iid sample from a population with mean $\theta$.</p>
<p>Now I am wondering about the intuition behind $E(X_1| \overline X ) = \overline X$, the sample mean.</p>
<p>If we just consider $X_1$ (or any $X_i$ for that matter) we have that $E(X_1) = \theta$ as the expected value of a... | 74,333 |
<p>There is a situation explained below where I intend to apply MLE.</p>
<p>The problem statement is that I am estimating a measure $X$.
This measure is obtained my Maximum Likelihood estimation technique. </p>
<p>I will apply this measure to an AR(2) model to find the parameters of AR model. The way the measure is ... | 74,334 |
<p>I'm struggling with mathematics behind linear regression. In the following lines I pasted the text from the book <a href="http://rads.stackoverflow.com/amzn/click/0387310738" rel="nofollow">Pattern Recognition and Machine Learning</a> (p. 46) where author derives the regression function $\mathbb{E}_{t} [t | \mathbf{... | 74,335 |
<p>I have a list of parameters which correlate with 1-2 covariates that I want to control for.</p>
<p>Following normalization, I wanted to do comparisons between groups, correlation analysis and probably use some of them as features in a prediction model.</p>
<p>The problem is that I don't think I can use the normali... | 74,336 |
<p>Let us suppose that I have a number of features. I design pdfs for every feature and every class, some of them by smoothing some histogram of training samples, others just by introducing the prior knowledge on how the feature should look like.</p>
<p>Now I want to know which is the most likely class for a given obs... | 74,337 |
<p>Below is a function I wrote to try and tune the $\lambda$ and $\alpha$ elastic net GLM implemented with <code>cv.glmnet</code>. I've noticed that the qualitative outcome (in terms of the alpha that yields the lowest prediction error score) changes depending on the random seed, and I suspect this is mainly because th... | 37,185 |
<p>In many econometrics model, the changes in the response variables in certain intervals are more difficult than other intervals. But I believe this is often not considered when estimating the model. </p>
<p>For example, suppose $Y_{st}$ represents the proportion of students in a certain school $s$, passing a standar... | 74,338 |
<p>I have a list of numbers I need to group by similarity (differences being 1 between each). For example, in a list of [198, 202, 207, 218, 219, 220], 190 would be put into a list, 202 would be put into another list, 207, into a list, and 218 219 220 into another list.</p> | 74,339 |
<p>I am struggling already a couple of days with this simple OLS, can you help?</p>
<p>Outcome years in function of predictor score, very simple linear model. The residual plot does absolutely not look good though. </p>
<p>Is it correct that based on the residual plot versus the outcome variable, to say that "if I pr... | 74,340 |
<p>This question is about three-way interaction and the possibility of applying without second lower terms with keeping the main variables in the equation not like the other questions. In fact the other answers suggest there is possibility of applying . I am not here to find the best solution because I know it and I al... | 49,556 |
<p>Which statistical tools are best suited for this problem:</p>
<p>Team A goes and measures 3 magnitudes in 200 locations (let's imagine the volume of a room, the insulation coefficient and the average temperature outside the room). For each room they calculate the energy this room will consume to keep the desired t... | 74,341 |
<p>I want to perform a repeated measures ANOVA in SPSS using the descriptive statistics. So my input is: </p>
<pre><code>Descriptive Statistics
Mean Std. Deviation N
M1MI 3,8000 1,03280 10
M1MA 5,3000 2,16282 10
M2MI 7,0000 1,88562 10
M2MA 2,2000 1,54919 ... | 37,190 |
<p>I am in a situation where I have to compute:</p>
<p>$$E(u(x_1)|\bar{X},S^2)$$</p>
<p>where $X_1$ is a normally distributed random variable and $u(.)$ some function. I know that by the student's theorem the sample mean and the sample variance are independent and moreover that $\frac{(n-1)S^2}{\sigma^2}\sim \chi^2 (... | 74,342 |
<p>I have a data set with ~80 records, with ~8 features. I want to predict one of the features in future records. The feature is numeric and discrete. It ranges between -30 up to 140 with steps of 5. Until now I wanted to predict another feature which is boolean, so I used logistic regression.
Which method should I us... | 20,432 |
<p>I am looking at a Semivariogram. I know it shows me the relationship between distance and semi-variance. I also know that at the end of the range the distance no longer auto correlates. What I am wondering is, what does the semi-variance tell me at the point where to distance no longer auto correlates (at the sill)?... | 74,343 |
<p>I'm trying to estimate how many people visited the farmers market once, twice, thrice, etc. in a given time period, using sampled data. We have interview data from approximately 50% of visitors as they entered the market which lets us identify them uniquely. For the purposes of this analysis, I'm assuming that the i... | 48,928 |
<p>It is standard advice to set a random seed so that results can be reproduced. However, since the seed is advanced as pseudo-random numbers are drawn, the results could change if <em>any</em> piece of code draws an additional number.</p>
<p>At first glance, version control looks to be a solution to this, as it woul... | 48,930 |
<p>Given an analysis of every pair of competitors in a race, how may I determine the probability of any given competitor winning the race?</p>
<p>For example, what is the probability of competitor 2 winning the following race? P(Cx Win) means the probability of Competitor x winning.</p>
<pre>
Cx Cy P(Cx Win) P(... | 5,024 |
<p>Diallel Analysis using the Griffing and Hayman approach is so common in plant breeding and genetics. I'm wondering if someone can share R worked example on Diallel Analysis. Is there any good referenced book which covered worked examples? Thanks</p>
<p>References:</p>
<p>Griffing B (1956) Concept of general and sp... | 37,194 |
<p>I've been aching to get my feet wet with a machine learning project, and I've found one that should be relatively simple, and actually has non-negligible business value for my organization. The marketing guys have to remove bot activity from our tracking data by hand for their metrics. I wanted to pull some data fro... | 74,344 |
<p>For given cost function $S(\beta) = (Y - X \beta)^T(Y - X \beta) + \lambda \beta^T \beta$, where $\lambda$ is regularization parameter, the $\beta$ that minimizes the given cost function is $\beta = [X^T X + \lambda]^{-1} X^T Y$.</p>
<p>is it right? </p> | 48,943 |
<p>I'm looking for a dataset (preferably with a story, at any rate a real dataset)
where a SVM with a linear kernel performs well...in other words i'm looking for
a dataset where the class boundary is likely to be linear. Ideally, there should
be between 10-20 continuous variables and not too many discrete ones....... | 74,345 |
<p>I have multiple logistic regression models with all of the same IVs/controls and a variety of DVs (all health outcomes from the same sample). The primary IV is the sum of types of childhood abuse (emotional, physical or sexual). I made dummy variables that represent any one type of experience, any two types of exper... | 48,944 |
<p>I'm trying to do a simple scatterplot and trend line in R, but it doesn't look right. Have I messed up something blatantly obvious? Any ideas as to why the line doesn't fit the data?</p>
<p><img src="http://i.stack.imgur.com/AISqZ.png" alt="the trend line does not fit the data"></p>
<p>Here is the code I used.</p>... | 74,346 |
<p>I am using two-samples paired permutation tests with Matlab. Now I have three within subject steps, forcing me to use a three-samples paired permutation test. Is there anything like that or any permutation test in general, I could use for that?</p> | 74,347 |
<p>I'm looking to generate a set of 5 random variables and enforce a dependence structure between them and onto a dependent variable Y. I understand how to generate correlated random variables for multivariate normal, but not when mixing different types. Below is a little more than I need, but I'm hoping someone can ... | 47,462 |
<p>Let's say I have a sample of "events" done by a certain number of subjects, and some (although not most) of these subjects have underwent more than one event. I'd like to fit a logit model to these data to find out which characteristics contribute to a subject, over the course of an arbitrary period of time, undergo... | 74,348 |
<p>I am trying to use the <code>glmnet</code> MATLAB package to train my elastic net model on some huge data. My features are of size 13200, and I have around 6000 samples of these. I directly tried to use <code>lassoglm</code> in MATLAB with these features and corresponding target taking cross validation to just 3 fol... | 37,201 |
<p>I am very new to Bayesian inference and can't figure out what may be an elementary problem. Also, please forgive me if I am screwing up the notation -- this is my first foray into Bayesian statistics.</p>
<p><strong>Set-up:</strong> At time $i=0$ I start with a random variable $X_0\sim \mathcal{N}(\mu_0,\sigma^2_0... | 48,959 |
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