question stringlengths 37 38.8k | group_id int64 0 74.5k |
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<p>I am conducting a least square regression using the python library numpy. When I run OLS (ordinary least square regression) over just the variable IE6 I get this output (with the key takeaway being that the coefficient is negative):</p>
<pre><code>====================================================================... | 71,263 |
<p>I've tried to use R to fit some longitudinal models, mostly via <code>lmer</code> and <code>nlme</code> packages. However, it seems that many standard models are lacking, such as antedependence models or factor analytic models for covariance matrices. These models are readily available in SAS. </p>
<p>Would anyone ... | 71,264 |
<h3>Scenario:</h3>
<p>An industrial/organizational psychologist is interested in determining whether adding 15-minute breaks increases worker productivity.
She selects a sample $n$ and measures productivity (on a continuous scale) before and after introducing the intervention.</p>
<p>The researcher runs a repeated m... | 71,265 |
<p>I have a time-series NDVI image. The image has 26 bands. 26 bands mean that images taken in 8-day time interval and counted in Julian days (97 to 297). For example; first band of the image is NDVI image at Julian date of 97, second is 105 etc until Julian day of 297. The image size is 12618, 4144. I have chosen 30 p... | 71,266 |
<p>Does anyone know a paper that describes the differences and compares the different deep learning architectures? like Stacked autoencoders, deep believe networks, maxout networks ... etc.</p> | 32,624 |
<p>I am doing factor analysis with Principal component extraction method.</p>
<p>Below is the Structure matrix</p>
<p>Extraction method: PCA</p>
<p>Rotation method: Promax with kaiser normalization
....................................................................COMPONENT............................................. | 32,625 |
<p>I have a decision support system that recommends Treatments (<code>T1</code> to <code>T8</code>) to patients, where <code>T</code>'s are nominal (i.e. no ordering or rating between them). I compare the system recommendations with the recorded treatments in a confusion matrix, where the columns list computer recommen... | 71,267 |
<p>Is it possible to obtain the effect size of a mediation with a binary outcome? I am
looking to report an effect size specifically for the indirect effect. I have already reported the effect sizes of the individual effects.</p>
<p>For example:
x = continuous IV - How connected to nature
M = continuous mediator - How... | 71,268 |
<p>I would appreciate some help comprehending a logical step in the proof below about the consistency of MLE. It comes directly from Introduction to Mathematical Statistics by Hogg and Craig and it is slightly different than the standard intuitive one that makes use of the Weak Law of Large Numbers. </p>
<p>So here go... | 32,629 |
<p>One of my variables has a low Cronbach's Alpha. I continued to run an planned contrast to test my hypothesis and the results were significant. </p>
<p>I understand that the results should be interpreted lightly. My question is however, what does it mean if the Cronbach's Alpha is low yet significant results have be... | 71,269 |
<p>I'm studying R package dlm. So far it seems very powerful and flexible package, with nice programming interfaces and good documentation.</p>
<p>I've been able to successfully use dlmMLE and dlmModARMA to estimate the parameters of AR(1) process:</p>
<pre><code>u <- arima.sim(list(ar = 0.3), 100)
fit <- dlmML... | 71,270 |
<p>Does anyone know where can I find a pseudo code or Matlab Code for CHMMs please?</p>
<p>I am using categorical observations. </p>
<p>Thanks. </p> | 71,271 |
<p>Suppose I have a $d \times n$ matrix $\mathbf X$ (each entry point has $d$ dimensions) and after some manipulation of data (i.e. summarizing the data $\mathbf X$) I get its $d \times d$ symmetric, quadratic <a href="http://stat.ethz.ch/R-manual/R-patched/library/stats/html/cor.html" rel="nofollow">correlation matrix... | 71,272 |
<p>My logistic model <a href="http://stats.stackexchange.com/q/48739/5509">has been suspicious</a> due to enormous coefficients, so I tried to do a crossvalidation, and also do a crossvalidation of simplified model, to confirm the fact that the original model is overspecified, as <a href="http://stats.stackexchange.com... | 45,824 |
<p>I want to develop an implementation of the grammar of graphics in python, and I need to wrap my head around a few things. I am actually having some difficulties in understanding some of the book's broadest concepts.</p>
<p>For what I understand, a correct implementation of the grammar means that a graphic is define... | 47,525 |
<p>I'm pretty new to statistics in general; maybe someone can edit the title to provide a better idea of my question.</p>
<p>The data I'm working with represents refined data extracted from browser log files gathered in a lab study. The probands solved three different types of tasks (let's call them a, b and c) and th... | 71,273 |
<p>I want to test the following hypothesis:
$$ H_0: \mu \geq \mu_0 \\
H_a: \mu < \mu_0.$$</p>
<p>I use one sample t-test:
$$t_0 = \frac{\bar{X} - \mu_0}{S/\sqrt{n}}.$$
Since under the alternative we expect that $\bar{X}$ is small, we should reject for small values of $t_0$. Thus, given that the size of the test is ... | 30,590 |
<p>Let's say that N randomly chosen persons where asked a question where the answer could be in either of X categories. For example, 500 persons where asked which of the top 5 political parties they support the most. Each person can give only one answer.</p>
<p>How do I determine if the leading party which, for exampl... | 32,638 |
<p>Let $T_1, T_2, \dots$ be iid sequence of exponential random variables with parameter $\lambda$. The sum $S_n = T_1 + T_2 + \dots + T_n$ is a Gamma distribution. Now as I understand the Poisson distribution is defined by $N_t$ as follows:</p>
<p>$$N_t = \max\{k: S_k \le t\}$$</p>
<p>How do I formally show that $N_t... | 71,274 |
<p>Im trying to use silhouette plot to determine the number of cluster in my dataset. Given the dataset <strong>Train</strong> , i used the following matlab code </p>
<pre><code>Train_data = full(Train);
Result = [];
for num_of_cluster = 1:20
centroid = kmeans(Train_data,num_of_cluster,'distance','sqeuclid')... | 71,275 |
<p>I've got a problem choosing the right model. I have a model with various variables (covariables and dummy variables). I was trying to find the best size for this model, so I first started by comparing different models with AIC. From this it followed, that the minimum AIC was reached when allowing all variables to st... | 43,478 |
<p>I am currently analyzing some data for my Master Thesis. I measured the dependent and independent variable in 2012 and also 2013. Now I want to see whether X (independent) has an impact on y (dependent). I thought about doing a correlation. However, I am not sure about this because it is measured at two points in ti... | 71,276 |
<p>There seem to be two different algorithms for comparing three or more survival curves using the logrank test.</p>
<p>Algorithm A. Found in books by <a href="http://rads.stackoverflow.com/amzn/click/0412276305" rel="nofollow">Altman</a> and <a href="http://rads.stackoverflow.com/amzn/click/0470870400" rel="nofollow... | 45,461 |
<p>When is it appropriate to use time dummies in multiple regression analysis? I am using pooled ols, random effects model, and fixed effects model. I have a period of 3 years.
I don´t know whether it is corrected but I think that time dummies should be included when the period under investigation is large, at least l... | 260 |
<p>I've written the following code to fit $$f=a*sin(b*x+c)$$ for <code>x=linspace(0,4*pi,100)</code>. I know the form of the required function so I can use <code>fminsearch</code> to find the best coefficients. To be able to use <code>fminsearch</code> it's need to write a matlab function that for given values of <cod... | 71,277 |
<p>I was wondering if anyone could elaborate more on this statement which I came across whilst reading a book on non-linear mixed effects model. I know that you can have linear, generalised linear and non-linear mixed effect models. </p>
<p>The book says "mixed models are non-linear statistical models, due mainly to ... | 32,644 |
<p>I am trying to model some data regarding a predator prey interaction experiment (n=26). Predation rate is my response variable and I have 4 explanatory variables: predator density (1,2,3,4 5), predator size, prey density (5,10,15,20,25,30) and prey type (3 categories). I started with several linear models (GLM) and ... | 32,645 |
<p>Three components are randomly sampled, one at a
time, from a large lot. As each component is selected,
it is tested. If it passes the test, a success (S) occurs; if
it fails the test, a failure (F) occurs.
Assume that 80%
of the components in the lot will succeed in passing the
test. Let X represent the number of su... | 71,278 |
<p>Here are three different versions of Neyman-Pearson lemma. They differ in that the first two (books) ignore the case when the likelihood ratio equals the critical value, while the last one (Wikipedia) doesn't. I feel not ignoring is natural, because ignoring will leave the set where the likelihood ratio equals the c... | 71,279 |
<p>I'm reading the IPCC report on climate change from 2007.
In their <a href="http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-uncertaintyguidancenote.pdf" rel="nofollow">uncertainity guide</a> they make a distinction between <em>likelihood</em> and <em>levels of confidence</em>.
What's the difference between the t... | 71,280 |
<p>How do I get p-values using the <code>multinorm</code> function of <code>nnet</code> package in <code>R</code>?</p>
<p>I have a dataset which consists of “Pathology scores” (Absent, Mild, Severe) as outcome variable, and two main effects: Age (two factors: twenty / thirty days) and Treatment Group (four factors: in... | 71,281 |
<p>I am working on industrial output data and running a lot of tests for it, before I proceed to make an ARIMA model for it. </p>
<p>Before I do that, I need to decide whether or not to "log" the data. </p>
<p>I am having trouble spotting whether the data is growing exponentially or not. And even if it's not - it's l... | 49,869 |
<p>I have a dataset with explanatory variable $X$ and response variable $Y$. Besides, there is a two-level factor $S_{j}, j=1,2$. The random error variance might be different between these two strata. I am applying three models to a data set.</p>
<p>Model 1, simple linear regression model: $Y_{i}=\alpha+\beta\times X_... | 362 |
<p>I've been thinking about a regression model with dependent variable a ratio in the range [0-600+]. About 50%+ are 0 values though, 40%+ values [0-5], and a very small percentage of the values are higher than 5, so the picture is quite skewed. </p>
<p>I've been wondering what kind of transformation I need to do in o... | 71,282 |
<p>Heloo,</p>
<p>pleas help me</p>
<p>How to read files (text and excell) into R ?</p>
<p>pleas write full instruction.</p>
<p>Thank for help</p> | 71,283 |
<p>from a deck of 52 cards, 9 cards are drawn at random without replacement. If X and Y are the number of hearts and diamonds respectively. What is the joint probability of X and Y and also what is the probability of X being greater than Y?</p> | 32,651 |
<p>I'm sorry if this is some kind of standard exercise, but I just don't know how to search for it.</p>
<p>I have infinite amount of samples and I can measure two properties $A$ and $B$ for each sample. Chance to measure $A$ is $P(A)$ and for $B$ it's $P(B)$, both properties are independent. I take N samples and on $a... | 71,284 |
<p>I'm trying to do principal component analysis (PCA) in R using the prcomp function. My input is a large matrix of 1,188 observations (rows) and 15,462 features (cols). I input this to the function with option scale = TRUE. The PCA completed normally, and the loadings ($rotation of the PCA data frame) is a matrix of ... | 7,137 |
<p>I would like to cross-validate a linear model using 10-fold CV and calculate the average error rate using the RMSE. I am wondering if the cost argument is the right way to do it. </p>
<p>At least for me being not a statistician the help file is not clear. It states "A function of two vector arguments specifying the... | 71,285 |
<p>I am building a natural language understanding component for a dialog system. The input is a natural language sentence (usually a short one), and the output should be a set of zero or more classes from a pre-specified set. For example: </p>
<pre><code>input: "I offer a salary of 20000 per month for work as a progra... | 32,655 |
<p>If $X$ and $Y$ are two independent random numbers from the interval $(0,1)$, then what is the PDF of $U = -2 \ln X$ and $V = -2\ln Y$?</p> | 71,286 |
<p>I am considering using Python libraries for doing my Machine Learning experiments. Thus far, I had been relying on WEKA but have been pretty dissatisfied on the whole. This is primarily because I have found WEKA to be not so well supported (very few examples, documentation is sparse and community support is less tha... | 947 |
<p>I am working with a UK credit-union and we are looking to build a model to assess our credit risk and changes to this over time. We have a number of loans to borrowers who each have a credit rating (lets say these are banded A, AA, AAA, B, BBB, etc...). </p>
<p>The way I have proceeded so far is to get the history... | 71,287 |
<p>Data was collected on binary variable and continuous variable. The binary variable represents two groups.</p>
<ul>
<li>Group 1 has a sample size $n_1$ and mean $\mu_1$ on the continuous variable</li>
<li>Group 2 has a sample size $n_2$ and mean $\mu_2$ on the continuous variable</li>
</ul>
<p>The significance test... | 71,288 |
<p>What is the Jeffreys prior for the geometric distribution?</p> | 71,289 |
<p>I have a repeated data in 7 diffrent time and 4 group. my variable is Dichotomous (yes/no). How I can do it with spss? what non-parametric test could I use?</p>
<p>I appreciate your answers</p>
<p>Leili</p> | 71,290 |
<p>Does there exist a flavor of spectral clustering (graph construction, type of laplacian, et cetera) that results in a clustering (on arbitrary data sets) that is similar to the k-means clustering "in spirit", i.e. finds a partition of the data into isotropic high density regions? (Of course, I don't expect exact equ... | 32,660 |
<p>I wish to perform a number of tests, what are the minimum number of tests I need to perform to be 95% sure the mean of the test is significant to within ±10% when I repeat the test ?</p>
<p>As one example, I wish to sample the mean time to set up a phone call and assume the set-up time is normally distributed. How ... | 71,291 |
<p>What is the relation between a dimension and a component in a Gaussian Mixture Model? And what are the meanings of dimension and component? Thank you.</p>
<p>Please correct me if Im wrong: my understanding is the observed data have many dimensions. Each dimension represents a feature/aspect of the collected data an... | 47,650 |
<p>[A duplicate thread can also be found at <a href="http://mathoverflow.net/questions/131142/finding-conditions-on-unspecified-cdf-that-permit-a-solution-to-an-equation" rel="nofollow">http://mathoverflow.net/questions/131142/finding-conditions-on-unspecified-cdf-that-permit-a-solution-to-an-equation</a> ]</p>
<p>Let... | 47,653 |
<p>I assume that using standardized regression coefficients is a way to compare the relative effect of two or more predictors (measured on different scales/units) on the mean value of Y.</p>
<p><strong>If you have several predictors that are comparable without standardization, and you transform one predictor to correc... | 32,662 |
<p>I'm trying to model a system given as a project, any help or advice is useful for now.</p>
<p>Here our assumptions for a part of it:</p>
<ul>
<li>If I study for the finals and do assignments, I have $80\%$ chance to get a scholarship</li>
<li>If I neither do assignments nor study, my chance reduces to $20\%$</li>
... | 32,663 |
<p>I have the occasion to sit in a Starbuck's almost every day. I have noticed there are rush hours sometimes. It's like hundred of people decided to buy something at Starbucks at the very same time. They rush in, the line becomes longer and longer, and about 15 minutes later they disappear until the next rush hour st... | 71,292 |
<p>I have been using the box-cox transformation to normalise data for input to an Ecological Niche Factor Analysis software, as recommended by the software creators.</p>
<p>However, it has occurred to me that the box-cox transformation method has (obviously!) been selecting different lambda values for each transformat... | 47,674 |
<p>I run the following SAS model:</p>
<pre><code>PROC MIXED DATA=dat order=formatted ;
CLASS LOT DOSE ;
MODEL TITRELOG10 = DOSE / s DDFM=KR ;
RANDOM DOSE / subject=LOT type=UN ;
RUN; QUIT;
</code></pre>
<p>and it yields the following results:
<img src="http://i.stack.imgur.com/saTzJ.jpg" alt="results_UN"... | 8,803 |
<p>My goal is to use the coefficients derived by previous research on the subject to predict actual outcomes given a set of independent variables. However, the research paper lists the Beta coefficients and t-value, only. I would like to know if it is possible to convert the standardized coefficients to unstandardized ... | 71,293 |
<p>Given two independently constructed <a href="http://en.wikipedia.org/wiki/Brownian_bridge" rel="nofollow">Brownian bridges</a> (from their marginal means and variances), is there a way to correlate the sample paths? </p> | 8,807 |
<p>Does anyone know of a reference for an expression for the Kullback-Leibler divergence between two Lomax (Pareto II) distributions? Not really worried which way the Lomax is parameterized. </p> | 71,294 |
<p>PROC MIXED in SAS sometimes estimates a non-positive definite matrix of the random effects. However PROC MIXED nonetheless provides the estimates and the standard errors of the fixed effects in such a case. Can we consider that these estimates and standard errors are correct ?</p> | 37,431 |
<p>As it is said, a picture is worth 1000 words. I have some data, and I need to put them in the right chart representation. </p>
<h3>The working scenario is this:</h3>
<p>some users have to predict how much internet bandwidth they will consume during 13 weeks. The users can form groups in order to buy more cheaper ... | 71,295 |
<p>I have a large scatterplot, with about 100,000 (x,y) points. The x coordinate is the set of numbers from (1 to ~100,000) - in other words, no 2 points have the same x-coordinate. The y is mostly constant (around 50-70 in value), but there are key "regions" where the y value spikes to ~120 or drops to ~20. How would ... | 32,673 |
<p>I'm already done in conducting the whole LAR Algorithm using lars() function in R Studio. But my problem is how to extract or use AIC in R Studio for choosing enough the number of variable that will explain my model. If i will use the predict.lars() function, only the Cp Criterion will appear. Anybody? Thank you in ... | 32,675 |
<p>Anyone could give me the whole Lasso Algorithm? The step by step procedure in determining Lasso solutions? I barely need this for my thesis. Thank You.</p> | 71,296 |
<p>I have a process in which X is a molecule going through birth ($x \rightarrow x + 1$) and death $(x \rightarrow x - 1)$. Rate of both reactions, namely synthesis rate for birth and elimination rate for death reaction, are proportional to number of molecules of X ($[X]$) at any given time.</p>
<p>In this system, ass... | 71,297 |
<p>The Stoppa distribution is a 3-parameter distribution that generalizes the Pareto distribution, adding a second shape parameter but no location term. The CDF is </p>
<p>$$F(x) = \left[1-\left(\frac{x}{x_0}\right)^{-α}\right]^θ;\quad 0 < x_0 \leq x$$</p>
<p>Definition from Kleiber & Kotz (2003). This dis... | 32,676 |
<p>I have developed a prediction model prototype in R. The model uses Support Vector Regression to predict. But I need to develop the entire solution in Visual C++ for a real life implementation.<br>
I have prior experience of coding normal regression equations for implementation.</p>
<ul>
<li>For Example: <br/> ... | 32,677 |
<p>I have a between-subjects ANCOVA (factors A and B, and covariate C), for which A*B is significant. I decomposed the interaction with a planned comparison described by the contrast A=(-1,1), B=(0,1), which was significant. I would like to find out the effect size (partial eta squared) for this effect, but unfortunate... | 71,298 |
<p>I have a R script which does some statistical modelling. I would like to expose this script as web service method which I would consume from a mobile application. How can I achieve this?</p> | 71,299 |
<p>I'm working with pandas and scipy, and I would like to find a quick way to visualise unusual values in a contingency table. </p>
<p>Say this is my contingency table:</p>
<pre><code> wolves lions tigers chickens total
ate_zebra 14112 13891 12978 54 41035
ignored_ze... | 71,300 |
<p>I am new to machine learning in R. This is my data set.</p>
<pre><code>channels<-sample(c("AFFILIATE","DIRECT","DISPLAY"),100,T)
booking<-sample(c("N","Y"),100,T)
placements<-sample(c("R","L","TR","TL"),100,T)
site<-sample(c("www.google.com","www.yahoo.com"),100,T)
campaigns<-sample(c("camp1","ca... | 6,266 |
<p>I went to a short talk and the speaker quickly mentioned something like 'LDA (linear discriminant analysis) is more likely to be overfitted than SVM (support vector machine)'. Is this true? And why?</p> | 3,519 |
<p>I realize that the divisions are meant to take into account the number of factor levels (which will tend to push up $\text{SS}_\text{between}$), and the number of observations (which will tend to push up $\text{SS}_\text{within}$). However, I can't understand why we don't obtain these Mean Squares by dividing $\text... | 71,301 |
<p>I have designed a questionnaire which has 16 Likert item questions; from 1 (strongly disagree) to 5 (strongly agree). The 16 Likert item questions are divided into 2 groups: 10 questions for customer loyalty, and 6 for customer satisfaction. </p>
<ul>
<li><strong>How do I know whether the Likert items should be gr... | 71,302 |
<p>Does it make sense to use cross-validation with factor variables that have 3+ levels? When using bestglm, I get an error saying that it doesn't work with categorical variables. In the documentation the reasoning is "Cross-validation is not available when there are categorical variables since in this case it is likel... | 32,681 |
<p>I am trying to model the prices of four energetic commodities with ARIMA models in R. Unfortunately the price series is not regular, as for some days, like Christmas, no price is given. My series is made of 2277 days(no weekends) and I have 81 days where the prices of all the commodities don't exist. Moreover the m... | 71,303 |
<p><img src="http://i.stack.imgur.com/Ruk10.png" alt="enter image description here"></p>
<p>This is my barplot. Model(red) is my estimated frequency at each X-axis vale (0-19) and actual is the frequency at each X-axis vale. How I can measure error of this estimating work in barplot?<br>
If I use mean percentage error... | 71,304 |
<p>I'm sorry I make reference to Stata here, but it's just to illustrate the point, the question is about whether it is correct or not using lagged variables in interaction terms.</p>
<p>I have a linear model that I am estimating using FE and RE, in which my explanatory (continuous) variable is lagged, something like... | 71,305 |
<p>The problem that we have is as follows. We have close to 60 discrete random variables each of which shall take on an average of 5 categorical values. We have developed a Bayesian network representation using our domain knowledge. We have the data for these 50 discrete random variables and how they interplay with eac... | 71,306 |
<p>I have training data set with around 1500 positive set samples and 4500 negative set samples. All the features are numeric( floating or integer type values) and the data is specific to bio-informatics domain. I have tried using SVM and random forest, both give me an accuracy of around 88% on test set of size 700 and... | 71,307 |
<p>I have some concerns regarding factor analysis and especially about combining the factor analysis for an ordinal scale (categorical data) - CATPCA with conventional PCA or with factor analysis. Basically, I need to enter my set of variables in CATPCA, take the transformed variables from CATPCA and introduce them in ... | 6,268 |
<p>I have build a sentiment index and am now validating its statistical properties and significance. I stumbled upon two problems.</p>
<p>(1) <code>dfgls</code>indicates that my sentiment is non-stationary as the t-statistics are all above (less negativ) than the critical value. Accordingly, I use the first difference... | 71,308 |
<p>I need to estimate an equation using some iterative method to optimally choose the coefficients. I won't go into the reasons that I can't use a simpler method like OLS, GLS or instrumental variables (it's a long, sad story). </p>
<p>My question is about whether I can expect equivalent results from <code>ml</code> a... | 71,309 |
<p>I'm currently working with postgresql on an amazon server ec2 and was wondering what is a good language to represent statistical analysis? I've been told that R is the best but heard from one experienced programmer that R runs slow when trying to display it on a website. I'm trying to perform some statistics with ... | 71,310 |
<p>I am reading Judea Pearl's "Causality" (second edition 2009) and in section 1.1.5 Conditional Independence and Graphoids, he states:</p>
<blockquote>
<p>The following is a (partial) list of properties satisfied by the
conditional independence relation (X_||_Y | Z). </p>
<ul>
<li><strong>Symmetry:</stron... | 71,311 |
<p>I am working on Gaussian Bayesian Networks (GBN) i.e. the Bayesian Networks where all the random variables are continuous in nature. I am seriously trapped in the problem of evidential reasoning in case of GBNs. Can anybody help me by guiding me regarding </p>
<ol>
<li>whether there are any established algorithm fo... | 71,312 |
<p>I am running a negative binomial regression of clinic counts in each county in the entire country (~3k counties). I'd like to at least partially account for the non-independence of neighboring counties by bootstrapping the confidence intervals in a "clustered" fashion--e.g. draw an entire state's (50 states total) ... | 71,313 |
<p>i and another coder want to assess our agreement.</p>
<p>our experiment involves coding the utterances of participants. there are 17 different codes that can be assigned, and we have independently counted their frequencies. </p>
<p>participant 1 may have uttered code 1: 3 times, code 2: 2 times, code 3: 1 time, an... | 48,426 |
<p>I tested 5 objects with two different devices each, but on the last test for the second device, there was an error so the value was unusable (ie on objects 1-5, first device series was 1,1,2,2,3 and second series was 1,2,2,2,X). Should I use n=5 for the first device and n=4 for the second device and use an unpaired... | 44,017 |
<p>I'm trying to use some form of survival analysis (e.g. accelerated failure time or proportional hazards) to study seed germination time. My data is interval censored (also called "grouped-time") and has a random effect (also called "frailty"). How can I do this, ideally in SAS?</p>
<p>My seeds were on petri dishes ... | 47,889 |
<p>I want to calculate the exponent of the function which shows zipf's law in data.
I'm working in the context of graph node degree analysis and want to comprehend results shown by <a href="http://www9.org/w9cdrom/160/160.html" rel="nofollow">Border et al.</a> on a new dataset. I have pairs of values where the first va... | 71,314 |
<p>My data has following distribution:</p>
<p><img src="http://i.stack.imgur.com/Hgwys.png" alt="enter image description here"></p>
<p>I wish to determine if it is a Normal distribution, so:</p>
<pre><code>> library(nortest)
Warning message:
package 'nortest' was built under R version 2.12.2
> sf.test(y)
Erro... | 71,315 |
<p><em>I am trying to figure out why calculating the SE directly in 22-4 gives me a larger result than that given in the solution</em> (examples change slightly each time the page loads):
<a href="http://www.stat.berkeley.edu/~stark/SticiGui/Text/standardError.htm#SE_of_RV" rel="nofollow">http://www.stat.berkeley.edu/~... | 71,316 |
<p>I'm trying to calculate the finite integral for the <a href="http://en.wikipedia.org/wiki/Standard_normal_distribution#Cumulative_distribution_function" rel="nofollow">CDF of the normal distribution</a>, when I plug the equation into Wolfram Alpha and integrate </p>
<blockquote>
<p>exp((-t^2)/2) dt from -inf to 1... | 32,701 |
<p>I've been working on Griddy Gibbs sampler (paper: <a href="http://www.jstor.org/discover/10.2307/2290225?uid=3738032&uid=2&uid=4&sid=47698747030947" rel="nofollow">Ritter and Tanner</a>) and I've implemented it in R. But I've faced a problem when I started thinking on its uses in other contexts. </p>
<p... | 71,317 |
<p>I'd appreciate any help on the following problem:</p>
<p>Let $X_1, X_2, \dots, X_N$ be i.i.d. continuous random variables with support $[0, 1]$.</p>
<p>What is a reasonable bound on the probability that some pair of random variables is less than $\epsilon$ apart? Mathematically, I'd like to find some $\delta$ not ... | 32,703 |
<p>I have a time series data for shipment with following variables:</p>
<ol>
<li>Year: 2008, 2009, 2010, 2011, 2012, 2013</li>
<li>Month: jan, feb, ..., dec</li>
<li>Number of ordering days</li>
<li>Shipment Volume</li>
</ol>
<p>I want to know the effect of the number of ordering days on the shipment volume.</p>
<p>... | 71,318 |
<p>Prove the following is equivalent to the Accept - Reject (AR) algorithm.</p>
<ol>
<li>Generate $X \sim g$;</li>
<li>Generate $U|X = x \sim U_{[0; Mg(x)]}$;</li>
<li>Accept $Y = X$ if $U \le f(x)$</li>
<li>Return to 1. otherwise.</li>
</ol>
<p>Attempt:</p>
<p>To prove the equivalency, I must prove that $f(x)$ is t... | 71,319 |
<p>In (most of) the analytical chemistry literature, the standard test for detecting outliers in univariate data (e.g. a sequence of measurements of some parameter) is Dixon's Q test. Invariably, all the procedures listed in the textbooks have you compute some quantity from the data to be compared with a tabular value.... | 71,320 |
<p>Consider a univariate normal model with mean $µ$ and variance $τ$ . Suppose we use a Beta(2,2) prior for $µ$ (somehow we know µ is between zero and one) and a $log-normal(1,10)$ prior for $τ$ (recall that if a random variable $X$ is $log-normal(m,v)$ then $log X$ is $N(m,v))$. Assume a priori that $µ$ and $τ$ are in... | 71,321 |
<p>Is there a package for Conditional autoregressive models in R (CARR). I need to use it for stock market forecasting and to compare with GARCH. </p> | 71,322 |
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