question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>Can anybody tell me how to find numerical values for standard errors of the MLEs of Weibull distribution using the uncensored real data set on the breaking stress of carbon fibres (in Gba) reported by Cordeiro GM, Lemonte AJ. The β-Birnbaum–Saunders distribution: an improved distribution for fatigue life modeling. C... | g64635 | [
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<p>I have one year of daily data for forecasting. while using auto.arima to find the best fit model, it gives me ARIMA(3,1,3). However, when I used tbats to find the best fit model, it gave me the following:</p>
<p>BATS(1,{2,2},-,-)</p>
<p>I wonder why they provided different models ( If I get it right, the BATS mode... | g22872 | [
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<p>I am working on a dataset which I am training using the Baum Welch algorithm in order to produce an HMM. Because of the fact that my dataset is rather small I am using Leave-one-out cross validation (LOO). Now, I need to decide an appropriate index for the goodness of fit.
The thing is that I cannot decide which is ... | g64636 | [
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<p>I have two correlated response variables ($y_1,y_2$) explained by the same covariate set ($x_1,x_2$), each with mean = 0.</p>
<p>I have a random grouping factor ('group') which is heteroskedastic ($group \sim N(0,\sigma^2_{u1})$ for $y_1$ and $group \sim N(0,\sigma^2_{u2})$ for $y_2$).</p>
<p>I would like to model... | g4567 | [
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<p>Background</p>
<p>I would like to measure the performance of a model trained on 3k samples, because this number of samples might be feasible to obtain in practice. I have a larger set of samples to choose from (about 25k), but generating the model is expensive in terms of time and computational effort, so I can onl... | g22874 | [
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<p>I have got data that looks like</p>
<pre><code>HAIR COLOUR SKIN COLOR NUMBER
"black" "brown" 1101
"red" "brown" 102
"yellow" "brown" 103
"black" "yellow" 1104
"red" "yellow" 105
"yellow" "yellow" 106
"black" "white" 1107
"red" "white" 108 ... | g22875 | [
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<p>For random variables $X \in \mathbb{R}^h$, and a positive semi-definite matrix $A$: Is there a simplified expression for the expected value, $\mathop {\mathbb E}[Tr(X^TAX)]$ and variance, $Var[Tr(X^TAX)]$? Please note that $A$ is not a random variable.</p> | g42729 | [
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<p>I am currently doing research on social media and how it can effect depression, anxiety and stress scale (DASS) scores. I have two age groups (18-25, 26-35) and also took scores on narcissistic personality inventory (NPI). I'm struggling to know what statistical test to do. I was thinking MANOVA with age as my indep... | g64637 | [
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<p>I'm trying to understand when credibility intervals are useful?</p>
<p>Are there examples of real world situations where credibility intervals are the better thing to use compared to confidence intervals? Note that by "useful", I mean maximizing some concrete real-world objective (so not for instance trying to get ... | g64638 | [
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<p>Do you know of any techniques that allows one to avoid and get rid of multicolinearity in SVM input data? We all know that if multicolinearity exists, explanatory variables have a high degree of correlation between themselves which is problematic in all regression models (the data matrix is not invertible and so on)... | g64639 | [
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<p>I'm using open source data to analyze innovation in a business context for my thesis. I've got the questions from the survey in an Excel file and although there's only 13 questions there's over 600+ variables and it is confusing for a beginning SPSS user like me. I want to see if there's a relationship between "inno... | g64640 | [
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<p>Consider a response <strong>y</strong> and data matrix <strong>X</strong>. Suppose I'm creating a model of the form - </p>
<p><strong>y ~ g(X,$\theta$)</strong> </p>
<p>(g() could be any function of X and $\theta$)</p>
<p>Now, for estimating $\theta$ using Maximum Likelihood (ML) method, I could go ahead either ... | g64641 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/12386/machine-learning-cookbook-reference-card-cheatsheet">Machine learning cookbook / reference card / cheatsheet?</a> </p>
</blockquote>
<p>There are numerous machine-learning approaches out there. Also ... | g49363 | [
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<p>I am having some trouble debugging an application of a linear discreet Kalman Filter. From time to time, I find that there are diagonal elements of the covariance matrix that become negative. This is clearly erroneous and causes the whole filter to blow up.</p>
<p>What are the possible causes and remedies for this ... | g64642 | [
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<p>I am studying for a test, one section of which will cover the delta method. This problem came from that section:</p>
<p>Let $X\sim N(\mu,n^{-1})$. Find an approximate distribution of $X^2$. (It also asks for exact distribution, but I can do that). </p>
<p>Can you help me get started? I can't see how I can apply de... | g42512 | [
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<pre><code>library(ltm)
fit <- rasch(LSAT)
factor.scores(fit)
</code></pre>
<p>This code can generate latent trait scores for response patterns. How can I extract latent trait scores for each observation? </p> | g42034 | [
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<p>I am trying to implement <a href="http://en.wikipedia.org/wiki/Apriori_algorithm" rel="nofollow">Apriori algorithm</a>. However I have a small doubt what to do when the same item appears more than once in the one basket,I have 2 transactions say </p>
<pre><code>T1 = {A,A,C}
T2 = {A,X}
</code></pre>
<p>What is the ... | g64643 | [
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<p>I am trying to introduce my data into SPSS. At the moment i am very confused. My questionnaire comprises 8 statements, where participants have ranked from strongly disagree to strongly agree their opinions. so far so simple. the only problem is, that for each of the 8 statements there are 8 characters that the parti... | g64644 | [
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<h2>Question</h2>
<p>A little something that I've been wondering about for a while:</p>
<p>Let $P_\theta$ be a stochastically increasing (one-parameter) exponential family on the sample space $\mathcal{X}$ with $\Theta\subset\mathbb{R}$ being its natural parameter space, i.e. $\Theta$ being the set of values for whic... | g64645 | [
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<p>I have likert scale responses (1-5 rating) of 20 respondents for a set of 25 questions. So that means that each respondent has answered 25 questions (with 1-5 rating). If I need to check the normality distribution of all the 25 questions together for a particular respondent, how do i do that?</p> | g64646 | [
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<p>I'm trying to simulate these two integrals using Monte Carlo simulation:
$$
\int_{-\infty}^\infty \exp(-x^2) dx, \quad \mbox{and } \int_{-\infty}^\infty \exp(-|x|) dx .
$$</p>
<p>When I use <code>runif(n,-Inf,Inf)</code>, I get <code>NaN</code> (number very close to zero) (using R).
I also tried converting that to... | g22503 | [
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<p>I have quite a few distributions that were generated by some system, and I am trying to find the probability of accordance to normality for these distributions. So, the probability of accordance to normality could be found as:</p>
<h1>P(p>0.05) = ( #p(AD test)>0.05 )/ total_no_of_distributions.</h1>
<p>where p(AD... | g64647 | [
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<p>I often hear people talking about neural networks as something as a black-box that you don't understand what it does or what they mean. I actually I can't understand what they mean by that! If you understand how back-propagation works, then how is it a black-box? </p>
<p>Do they mean that we don't understand how th... | g22886 | [
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<p>ok i am not a statistician.</p>
<p>I am doing paired comparison for several outcomes of cross validated interpolation results.</p>
<p>I have to consider only the absolute value in my analysis and so although original data follows a normal distribution the resultant absolute values are only half normal.</p>
<p>So ... | g64648 | [
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<p>Suppose I have a data frame such that:</p>
<pre><code>set.seed(2014)
df<-data.frame(y=rbinom(100,1,0.3),futime=as.integer(rnorm(100,100,10)),
age=rnorm(100,50,5),sex=rbinom(100,1,0.5))
df[df>100]<-100
</code></pre>
<p>where <code>y</code> is the outcomes and <code>futime<100</code> are right censo... | g64649 | [
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... |
<p>My understanding of some statistics: </p>
<p>For a given experiment a finite number of samples can be taken, defining the sample size. However this experiment may have an infinity large population size.</p>
<p>Given that in an infinitely large population size any possible outcome will occur an infinite number of t... | g64650 | [
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<p>I will mark this as homework, even though it's just general interest. The scenario is a little silly, because it's just a real world case for a theoretical problem I've been thinking about.</p>
<p>A man enters a hot dog eating contest every year and in the contest he has to eat 10 hotdogs in 5 minutes (yes it is di... | g64651 | [
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<p>What is the reason why we use natural logarithm (ln) rather than log to base 10 in specifying functions in econometrics?</p> | g42521 | [
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<p>Would it make sense to do a 2SLS regression for Nominal GDP and Money Supply (using predetermined variables of government expenditure and investment)?</p>
<p>If it does make theoretical sense, is this because GDP and Money Supply are endogenous? I am unsure why GDP is endogenous... For example if there is an increa... | g64652 | [
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<p>I've been working with PyMC for a bit, and am stuck on this one. I see example on fitting time series, in the tutorial and others like:</p>
<p><a href="http://lighthouseinthesky.blogspot.com/2011/10/curve-fitting-part-5-pymc.html" rel="nofollow">http://lighthouseinthesky.blogspot.com/2011/10/curve-fitting-part-5-p... | g42524 | [
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<p>i've got questions about clustered-stratified random sampling.</p>
<p>let's say I want to do a research in narcotics.</p>
<p>the population that I will be working with is a combination of academics, students, and government employees (law enforcers, DEA, etc). I consider the population's unknown because I couldn't... | g64653 | [
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0.033425454050302505,
0.04291258379817009,
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0.038791634142398834,
... |
<p>From a Physics equation I have the following model:</p>
<p>$$W=\beta_0+\beta_1Z$$</p>
<p>$\beta_0$, $\beta_1$ are fixed values for which I want to find a $1-\alpha$ confidence region.</p>
<p>I have $(z_1,w_1),(z_2,w_2),\ldots,(z_n,w_n)$ observations.</p>
<p>I get these observations from evaluating the function $... | g64654 | [
-0.003177955048158765,
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... |
<p>I'm looking to confirm whether having a 4 point Likert Scale for some constructs, and a 5 point Likert scale for other constructs will be suitable when developing a questionnaire?</p>
<p>I have 7 constructs with a 4-point scale, then 2 constructs with a 5 point scale and one construct with a different 4-point scale... | g22892 | [
0.025042621418833733,
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0.0011043917620554566,
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0.000407873623771593,
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0.023710669949650764,... |
<p>Given a large matrix with 10,000 rows (variables) and 20 columns (sampling timepoints), I am trying to build a linear model to find the sampling timepoint given some of the variables. So in essence, I want to find a small subset of variables that explains the data well enough that I can build a linear model like <co... | g64655 | [
0.009004436433315277,
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0.012705706991255283,
0.006401553750038147,
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<p>I'm curious if it's possible to predict the results of a pairwise comparison matrix that will be sent out to 100 people based on the results of one or two filled out surveys?</p>
<p><strong>The matrix has the following format:</strong></p>
<pre><code>Indicators Var_1 Var_2 ..... Var_n
Var_1 NA
... | g43057 | [
-0.024439411237835884,
-0.009339776821434498,
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0.028923677280545235,
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0.022008471190929413,
0.0007565007545053959,
0.03537364304065704,
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0.02891504392027855,
-0.... |
<p>I want to include 2 covariates that are group characteristics as fixed effects in predicting a variable that is at the individual level. How to include them in the lmer formula? At this point my random effects are given just by the intercept and my fixed effects are only individual level variables.</p>
<pre><code>a... | g64656 | [
-0.017551105469465256,
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0.007256955839693546,
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0.030099190771579742,
0.061998363584280014,
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0.030... |
<p>I am trying to use the Zelig package to create a linear model and perform 'what if' analysis and run a simulation to determine what the quantiles will be if give an value.</p>
<p>My data frame looks like this:</p>
<pre><code>dput(head(mydata, 10))
structure(list(DATE = structure(c(1367409600, 1367413200, 136741680... | g64657 | [
-0.00323768169619143,
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0.033518824726343155,
... |
<p>I know that the gamma distribution with parameters $k$ and $\theta$ can be used as a model for the occurrence of events. The requirement on the events would be that their occurrence is random and the mean time between them equals $\theta$ and that they belong to a Poisson process.</p>
<p>Now I have a question regar... | g64658 | [
0.04755954444408417,
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0.003740984946489334,
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0.0041104089468717575,
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-0.005850500892847776,
-0.0009694655309431255,
-0.008730285800993443,
-0.004674424882978201,
... |
<p>DISCLAIMER: This question was sent to Stata list today, but so far nobody has answered.</p>
<p>NOTE: I use Stata here, but actually I don't think the question is software-specific.</p>
<p>Hi,</p>
<p>I would appreciate someone could provide me an answer to the following question:</p>
<p>I am estimating the follow... | g22897 | [
0.00917855929583311,
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0.03915644809603691,
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0.024806292727589607,
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0.004675301723182201,
0.08012... |
<p><strong>Update (Sept 10, 2013)</strong>: I believe it would be more correct to say that increasing baseline or endline measurements are ways to decrease the design effect, thereby making the SW design efficient, rather than stating that the maximum number of measurements is necessary. <a href="http://www.ncbi.nlm.ni... | g64659 | [
-0.03533897176384926,
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0.039932359009981155,
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0.019008276984095573,
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0.036810215562582016,
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... |
<p>So I'm looking at student stigma affecting self-esteem. The overall idea is that stigma affects student achievement through the mediator self-esteem, so I will do multiple regressions and test for mediation. The issue here is that I want to look at moderators. I know that moderators can be gender and ethnicity. My q... | g64660 | [
-0.027707984670996666,
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0.040742237120866776,
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0.027746452018618584,
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0.013212169520556927,
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0.0369531586766243,
0.032062679529190063,
0.03... |
<p>So the background is that the I collected yield data for past 5-6 decades and location from where I collected yield data had high yielding varieties introduced over time. I am looking at the relationship between yield and rainfall but this introduction of HYV might affect the true impact of monsoon on yield and ther... | g64661 | [
0.05597132816910744,
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0.0006543868221342564,
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0.035593871027231216,
0.01033065002411604,
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-0.01777329482138157,
0.006111219059675932,
0.00815604254603386,
0.000590133189689368,
-0.03... |
<p>If I difference a time series and take out trend and seasonality ... does it mean we are left with only irregularity on which we plot the acf and pacf to arrive at the MA and AR order?</p>
<p>Do 1st difference, 2nd difference always detrend the series, or do we need to detrend separately?</p> | g16696 | [
0.044372424483299255,
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0.0329710878431797,
0.026813754811882973,
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<p>I have a process which generates a binary outcome from a multiplication of two independent stochastic binary inputs:</p>
<p>Out = X1(P1) * X2(P2) .</p>
<p>X1 and X2 generate a binary output with some probability, P1 and P2, respectively.</p>
<p>I have a set of examples, for which I know "Out" and P1. I would like... | g22902 | [
0.03386079892516136,
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0.020369965583086014,
0.014222771860659122,
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0.0372522808611393,
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0.013469682075083256,
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0.037042707204818726,
0.00438323337584734,
0.0325... |
<p>Why is the "de-facto" in statistics to minimize the sum of squared errors cost function instead of maximizing some reward function like the likelihood function?</p> | g64662 | [
0.02703915722668171,
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0.09772034734487534,
0.03... |
<p>Dear crossvalidated community,</p>
<p>quite frankly, I'm not that much into statistics and therefore, I'm having much trouble solving some issues im having in Matlab right now. My plan is to imitate/simulate some realistic driving patterns of costumer in a car sharing simulator. Therefore, I picked a logarithmic pr... | g64663 | [
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0.033368926495313644,
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0.0008244405617006123,
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0.0002704004873521626,
0.03732272982597351,
-0... |
<p>I'm about to do my analysis of my Master's thesis, but I have a question. I want to check whether media effects on political trust are different between natives and immigrants. These are my variables: </p>
<ul>
<li>Dependent: political trust (a continuous variable, ranging from 0 to 70 (I summed up seven items on... | g64664 | [
-0.020231781527400017,
0.030081473290920258,
-0.0304965078830719,
-0.036431796848773956,
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0.0009636062895879149,
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0.0007270440110005438,
-0.024562574923038483,
0.030548570677638054,
0.02042141929268837,... |
<p>I am working on time series. I have a set of data which I would like to use for estimation. Can some one tell me how to find under what distribution the data I have goes in. I tried plotting using </p>
<pre><code>histfit(data) in matlab
</code></pre>
<p>can some one help.
Thanks</p> | g64665 | [
0.04598717764019966,
0.003938212525099516,
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-0.027025269344449043,
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0.05020349472761154,
0.03003430739045143,
-0.0... |
<p>I'm currently using the Pearson (product-moment) correlation coefficient (PPCC) to look at the relationship between deprivation and healthcare usage in a population, but I think I've probably got this wrong.</p>
<p>The problem is that the population (about a million people) is broken up into about 100 geographical ... | g64666 | [
0.01770622469484806,
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0.002510176505893469,
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0.0007155412458814681,
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0.031052442267537117,
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-0.015248811803758144,
0.06740768998861313,
0.013499235734343529,
0.011838600970804691,
-0... |
<p>I transmitted 50 packets to receiver but few of them are missing and i assumed that missing probability of each packet is 0.1.Now i retransmit packet like-</p>
<p>1 0 1 0 1 1 1 0 1 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ------1st retarnsmission row</p>
<p>0 0 0 0 0 0 0 1 ... | g43743 | [
0.002872647251933813,
0.01287875697016716,
0.002309764502570033,
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0.07787314802408218,
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0.043887507170438766,
0.01607966236770153,
0.025580987334251404,
-0.033352550119161606,
-0.09288468211889267,
0.036383822560310364,
0.018502812832593918,
0.029... |
<p>I am basically a biologist working in genomic data analysis. I have started learning statistics and now am acquainted with basics of it. I can run several statistics commands on R. </p>
<p>I have plenty of pdfs which emphasise how to run R or how to perform statistical tests etc., but do not explain the output in a... | g22909 | [
0.033324774354696274,
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0.009305586107075214,
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0.009730891324579716,
0.0554107166826725,
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0.04540620371699333,
-0.038553... |
<p>I recently started trying to apply Gaussian process regression to a problem, using the MATLAB GPML toolbox. The problem has five (or more) input variables, but for now I'm just looking at one of them. </p>
<p>With manually selected hyperparameters, I get reasonable-looking output, but my problem is that when I <cod... | g64667 | [
0.007259989622980356,
0.008272901177406311,
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0.02874612808227539,
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0.012739446014165878,
0.021729599684476852,
0... |
<p>Suppose I have longitudinal data of the form $\mathbf Y = (Y_1, \ldots, Y_J) \sim \mathcal N(\mu, \Sigma)$ (I have multiple observations, this is just the form of a single one). I'm interested in restrictions on $\Sigma$. An unrestricted $\Sigma$ is equivalent to taking
$$
Y_j = \alpha_j + \sum_{\ell = 1} ^ {j - 1}... | g22912 | [
0.05898653715848923,
0.004039265215396881,
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0.015132510103285313,
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0.02303304150700569,
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0.014029284007847309,
0.015452144667506218,
0.08308596909046173,
0.05115... |
<p>This is a theoretical question.</p>
<p>Suppose that I have a sample s1 coming from distribution K, and a sample s2 coming from distribution M. But I don't know what K or M are. I hypothesize that s1 and s2 are coming from distribution T. I plug in s1 and s2 to pdf of T and calculate their likelihoods, say L(s1), L(... | g22913 | [
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0.01537499949336052,
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0.00288778287358582,
0.05585167929530144,
-0.0... |
<p>I am writing a report in which I have taken the incidents of bomb-blasts as the population and as the sample, I have taken the incidents in which there were some fatalities. kindly tell me which type of non-probability sampling is this?
Is it Judgmental sampling or Purposive sampling in which the researcher choose... | g22915 | [
0.024757355451583862,
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0.054792843759059906,
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0.011742630042135715,
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<p>I spent some time yesterday learning about Boltzmann machines (and their cousins, restricted Boltzmann machines). They seem interesting and very powerful, but one little thing is bugging me. </p>
<p>The energy function for a Boltzmann machine is (assuming the use of a bias node)
$$
E = -\sum_{ij} w_{ij} s_i s_j,
$$... | g64668 | [
0.0019012097036466002,
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0.029... |
<p>Consider two independent discrete random variables $y_1$ and $y_2$, both distributed with a Beta-Binomial distribution, with different number of successes $n_1$ and $n_2$ but the same parameters $a$ and $b$</p>
<p>$ p(y_1|n_1,a,b) = {n_1 \choose y_1} \dfrac{B(y_1 + a,n_1 -y_1 +b)}{B(a,b)} $</p>
<p>$ p(y_2|n_2,a,b)... | g22920 | [
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0.0027602980844676495,
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0.04036901891231537,
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<p>I'm trying to replicate models published in <a href="http://www.csef.it/WP/wp226.pdf" rel="nofollow">The Age-Productivity Gradient: Evidence from a Sample of F1 Drivers</a> and am stumbling at first hurdle over a line "the baseline specification contains a quadratic in age and drivers dummies".</p>
<p>I can get qua... | g64669 | [
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0.003737768856808543,
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0.03838510811328888,
0.05380861461162567,
-0.... |
<p>I realise there are other reasons why p-values will decrease with increased sample size, but I am wondering if this reason is valid at all.</p> | g64670 | [
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<p>We've got a construct-likert-scale with an internal (8 items) and an external dimension (6 item) and there is also a 5-point item y assessing the "subjective" perception (<em>How skilled do you think you are?</em>). </p>
<p>$N$ is 250 </p>
<p>y-Cell frequency:</p>
<pre><code>extrem gering sehr gering ger... | g64671 | [
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0.05856164172291756,
0.01710221916437149,
... |
<p>Assume that two r.v. $W$ and $Y|W=w$ with</p>
<p>(1) $W \sim \text{N}(\mu_w,\sigma_w^2)$ (iid)</p>
<p>(2) $Y|W=w \sim \text{N}(w,\sigma_y^2)$ (iid)</p>
<p>Further we only observe $Y$ if $Y$ is less then $W$, i.e., </p>
<p>(3) $Y|Y\le W$</p>
<p><strong>Goal:</strong> Find the pdf of the censored observations, i.... | g64672 | [
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0.028963211923837662,
-0.015072772279381752,
0.05033664032816887,
0.01907160133123398,
0.02... |
<p>How can I verify that </p>
<p>$\lim_{N,M,K \to \infty, \frac{M}{N} \to 0, \frac{KM}{N} \to \lambda} \frac{\binom{M}{x}\binom{N-M}{K-x}}{\binom{N}{K}} = \frac{\lambda^x}{x!}e^{-\lambda}$, </p>
<p><strong>without</strong> using <strong>Stirling's formula</strong> or the <strong>Poisson approximation to the Binomial<... | g64673 | [
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<p>Please, help me to understand how to compare two models - simple OLS and multilevel regression? Below you can see their pictures. In the simple regression there are 7 predictors including binary variable centr which is referred to central district of the city. In multilevel model I exclude centr and create the secon... | g64674 | [
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<p>Two questions:</p>
<p>a. Consider the regression y[i] = a + b x[i] + e[i]. Let bhat=(ols) estimate of b and xbar=sample mean of x. How to test the hypothesis (b*xu)=0? xu is the population mean of x.</p>
<p>b. Consider the regression y[i] = a + b x[i] + c z[i] + e[i]. Let bhat and chat be the (ols) estimates of b ... | g22924 | [
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<p>I have this example logit model where some of the variables are factors but I'm not too sure how to interpret the effects. If I understand logit models correctly the coefficients that we get from the fitted model are the change in log-odds per unit change in the explanatory variable holding everything else constant.... | g49702 | [
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<p>I am trying to match treatment with the control using the <code>R Matching package</code> for the data set nuclearplants (which is available in <code>optmatch package in R</code>). Following is the code for matching:</p>
<pre><code>library (optmatch)# for the dataset nuclearplants
library(Matching) # for performing... | g22930 | [
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<p>Background: Group A the control group uses a website 1. Group B the treatment group uses website B. The expected result is that Group B will have a higher understanding than group A. Hypothesis: The treatment group will show increased levels of understanding.
A 1(Strongly Agree) - 7(Strongly disagree) likert survey... | g64675 | [
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<p>I have two data sets in which the same Likert scale questions were answered by two different responders. I want to calculate which level they are correlated.
My data set is like</p>
<pre><code>WorkerID Question Worker_answer Employer_answer_about_his_worker
1 1 3 ... | g42564 | [
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0.07620377838611603,
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0.0182... |
<p>I have calulated an OLS with and without a constant term. However, besides that the values are different I haven`t really found anything valueable?</p>
<p>Therefore my question is:</p>
<p>Whats the biggest difference in calculating a simple regression model with/without a constant term?</p>
<p>I really appreciate... | g22931 | [
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... |
<p>I know that k-means is unsupervised and is used for clustering etc and that k-NN is supervised. But I wanted to know concrete differences between the two?</p> | g42566 | [
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<p>I was reading the user's guide of SPSS on missing value analysis and I found the terms monotonic and non-monotonic pattern of missing values. The terms are not quite clear to me. They used <code>telco_missing.sav</code> data file to show a graph from which they comment:</p>
<blockquote>
<p>If the data are monoton... | g64676 | [
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<p>I'm trying to run the following code in JAGS</p>
<pre><code>model {
for (i in 1:n){
z[i] ~ dnorm(X[i], tau)
X[i] <- D1*x1[i] + D2*x2[i] + D3*x3[i] + D4*x4[i]
}
denom <- 1 + sum(exp(p))
D1 <- (exp(p[1]))/denom
D2 <- (exp(p[2]))/denom
D3 <- (exp(p[3]))/denom
D4 <- 1/denom
# Prior for Fixed... | g22933 | [
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<p>I want to perform a t-test on two independent samples with each n = 50. to check the assumptions, I ran an F-test for homogenity, which is significant. then I used SPSS which does a levene test by default and this levene test was not significant. I don't have the data here, but n = 50 (data are rental prices) is pro... | g24659 | [
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<p>I am trying to interpret one of the p-values in a one variable linear regression. Some of the answers I've seen for similar questions were not worded as thoroughly as I would have liked. My interpretation is deliberately verbose because it will aid my understanding if faults are found within it.</p>
<p>From Micro... | g49294 | [
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<p>I know that this question is hard to answer, but I was wondering how you would determine if a statistical technique was in current use, or if it had a heyday a couple of decades ago but it's either been superseded by newer techniques or perhaps it was even proven to be inadequate and abandoned?</p>
<p>For example, ... | g64677 | [
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0.... |
<p>I have two continous samples: background and data. I want to check whether data observations are significantly greater than background. I used <a href="http://en.wikipedia.org/wiki/Mann%E2%80%93Whitney_U" rel="nofollow">U-Test</a> to calculate p-value, but now I want to find a pair of background/data with the bigges... | g64678 | [
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0.0375... |
<p>In regression, you encode a categorical variable with n possible values using n-1 indicator variables. How about for neural networks?</p> | g64679 | [
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<p>I’m trying to generate correlated random sequence with mean = $0$, variance = $1$, correlation coefficient = $0.8$. In the code below, I use <code>s1</code> & <code>s2</code> as the standard deviations, and <code>m1</code> & <code>m2</code> as the means. </p>
<pre><code>p = 0.8
u = randn(1, n)
v = randn(1,... | g49933 | [
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... |
<p>I am building a Cox PH model for recurrence-free survival from breast cancer. One of my variables, the number of involved lymph nodes, is highly skewed with many more "0" values than positive integers. It seems to me that this would make any transformation ineffective because this variable cannot be negative. Her... | g37930 | [
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<p>IN order to perform efficient coordinate descent, I am using SVD to diagonalize my system $$y=Ax$$ to
$$y=USV^Tx\\ U^Ty=y_{new}=S(V^Tx)=Sx_{new}\\
y_{new}=Sx_{new}$$
where $S$ is the diagonal matrix of singular values.
Now I can solve the system in parallel by just $x_i=\frac{y_i}{s_i}$.</p>
<p>The problem is, that... | g5023 | [
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<p>The questions on a survey asked:</p>
<ul>
<li>Do you actively participate in a study group?</li>
<li>Do you think the class is going too quickly?</li>
</ul>
<p>For both, the responses are one of the following: strongly agree, agree, neutral, disagree, strongly disagree</p>
<p>So I want to analyze if there is a co... | g64680 | [
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<p>I have met the theorem: </p>
<p>"For each stationary time series there is ARMA model with finite number of parameters."</p>
<p>Could you indicate official source with proof (bibligraphy) of this theorem?</p> | g22941 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/6350/anova-assumption-normality-normal-distribution-of-residuals">ANOVA assumption normality/normal distribution of residuals</a> </p>
</blockquote>
<p>I have a dataset storing measurements of seed area, c... | g49703 | [
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<p>Here's my experiment: I'm testing the physiological effects of a treatment on a mice (measuring continuous variables such as total mass, fat mass, bone density, etc). I want to test the significance of this treatment on weight gain parameters.</p>
<p>What I've done so far: in R, I've fitted a logistic glm model, us... | g64681 | [
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<p>I would like to compute belief intervals (confidence intervals; CI) for the parameters of an environmental dynamic model within the Bayes' theorem. The measurement model of the data is
$$
d(t)=y(\theta,t)+\epsilon,
$$
where $\epsilon$~Norm(0, $\sigma$) is the assumed measurement error, $y$ is the dynamic system ou... | g64682 | [
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<p>I am trying to derive a formula for my collaborative algorithm problem to calculate popularity rating of an item.</p>
<p>I am considering three factors to calculate rating for an item based on three different ratings $a$, $b$ and $c$, each with weight $w_1$, $w_2$ and $w_3$. The cumulative rating is:</p>
<p>$$w_1 ... | g49704 | [
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<p>Data can have trends, cycles, seasonal pattern repeats and irregular components. How do these components impact on the ordinary multiple regression with dummy variables?</p> | g64683 | [
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<p>Is this all I have to do to implement 2 fold stratified cross validation:</p>
<ol>
<li>Assign random number from uniform distribution [0...1] to each row.</li>
<li>Assign row to fold 1 if random number <= 0.5 otherwise assign to fold 2</li>
</ol>
<p>Does this ensure that the class priors are roughly the same in... | g64684 | [
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<p>Hey I have to regress abnormal returns for 202 companies over a period of 10 years (between 2004-2013) against their respective PE ratios and a Profitability measure for the same time period. Thus I have to run a pooled regression. I have read online on how to do it...but still am not sure of the process and also di... | g64685 | [
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<p>I have a Markov Chain such that $X_n = max(X_{n-1}+\xi _n,0)$ where the $\xi_n$ series is independent and identically distributed. I want to show that if $\mathbb E(\xi_n) > 0$ (where $\mathbb E(\xi_n)$ is the expected value of $\xi_n$) then$\frac{X_n}{n}$ tends to $\mathbb E(\xi_n)$ as n approaches infinity for... | g36007 | [
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<p>First of all, I'm fairly new to Decision Theory and my question might be rather too simple for the experts.</p>
<p>I am having some issues in computing confidence for A/B Testing. I will first explain the scenario and then the technique to compute confidence.</p>
<p>It's a typical scenario extending from clinical ... | g64686 | [
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0.05114831402897835,
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<p>For each round of bootstrapping (say $n=1000$), I would like to select the genotypes (the columns) at random without replacement from the original dataset. With this I would like to form two groups with 10 and 10 genotypes each to match the genotypes in $X$ and $Y$ subsets respectively.</p>
<p>With the original dat... | g64687 | [
-0.026402480900287628,
-0.011528144590556622,
0.013704637996852398,
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<p>I was asked about doing a power analysis of a seasonal kendall trend test. I feel like that would be really difficult to do and I haven't found any documentation or software on how to do it. Is there some way to estimate the required sample size using regression? Hopefully someone can point me in the right direction... | g22952 | [
-0.022248873487114906,
0.01423465833067894,
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-0.010663557797670364,
0.03382427617907524,
-0.010970719158649445,
0.04634683579206467,
... |
<p>I <a href="http://stats.stackexchange.com/q/4914/919">posted a question earlier</a> but failed miserably in trying to explain what I am looking for (thanks to those who tried to help me anyway). Will try again, starting with a clean sheet.</p>
<p>Standard deviations are sensitive to scale. Since I am trying to perf... | g64688 | [
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0.00837300717830658,
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0.0027706073597073555,
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-0.06361114233732224,
0.03874552249908447,
0.004106117878109217,
0.018597781658172607,
-0.01... |
<p>What I'm trying to do is predict some biodata based on time. Because the biodata are not normally distributed, I have modeled them with a poisson using a log link function ( E[y] = exp[BX]). What I'm trying to do is estimate the time at which the predicted curve reaches a certain threshold. (i.e., y=1 when x=?). Obt... | g64689 | [
0.01913670264184475,
0.020647147670388222,
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0.0015786410076543689,
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0.015204360708594322,
0.0161709226667881,
-0... |
<p>The system:</p>
<ol>
<li>I have a bag filled with 1,000 balls</li>
<li>All of them are either red or blue</li>
</ol>
<p>I want to gain some amount of confidence that all the balls are blue, but I'm very lazy and I only want to examine a sample as small as possible.</p>
<p><strong>Question: How large must the samp... | g64690 | [
-0.022802015766501427,
0.014336290769279003,
0.011957189999520779,
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0.0014221316669136286,
-0.01016584038734436,
0.022114314138889313,
0.004246223252266645,
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-0.005944001022726297,
-0.039007727056741714,
0.04006123170256615,
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0.... |
<p>The fisher linear classifier for two classes is a classifier with this discriminant function:</p>
<p>$h(x) = V^{T}X + v_0$
</p>
<p>where </p>
<p>$V = \left[ \frac{1}{2}\Sigma_1 + \frac{1}{2}\Sigma_2\right]^{-1}(M_2-M_1)$
</p>
<p>and $M_1$, $M_2$ are means and $\Sigma_1$,$\Sigma_2$ are covariances of the classes.... | g42593 | [
-0.00622888607904315,
-0.04563955217599869,
0.015354433096945286,
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0.06222880259156227,
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-0.008063076995313168,
-0.0442708395421505,
0.07412803173065186,
0.038862429559230804,
0.1... |
<p>I'm looking for a method to determine if a 2-d dataset forms a single cluster or is split into two/multiple clusters - and what's the likelihood or p-value for this. Isolated data should not be considered as different cluster. Also, data has a non-parametric distribution.</p>
<p>My approach is to apply an unimodal ... | g64691 | [
0.011649931780993938,
-0.006143849343061447,
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0.020026059821248055,
0.02270643226802349,
0.057820193469524384,
... |
<p>If two classes $w_1$ and $w_2$ have normal distribution with known parameters ($M_1$, $M_2$ as their means and $\Sigma_1$,$\Sigma_2$ are their covariances) how we can calculate error of the Bayes classifier for them theorically?</p>
<p>Also suppose the variables are in N-dimensional space.</p>
<p><strong>Note:</st... | g42595 | [
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... |
<p>I want to estimate the following model</p>
<p>$y_{it} = \gamma_{0} + \gamma_{1} x_{it} + \gamma_{2} \theta_{i} x_{it} + u_{it}$</p>
<p>where the $\theta_i$ is unknown but I can estimate it in another regression. Plugging in that estimate and rewriting the equation, I get</p>
<p>$y_{it} = \gamma_{0} + \gamma_{1} x... | g64692 | [
-0.02587088942527771,
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0.014090211130678654,
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0.03712932765483856,
0.015438119880855083,
0... |
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