# All Questions

16k views

### Filtering a dataframe

Still learning basic functions in R, The subset function seems to only filter based a condition based on single column with or without multiple conditions? How can I easily filter data from a ...
440 views

### Predicting number of events with 99.9% probability based on tests of four devices

I've never taken a stats course so I really don't know where to begin on this. I am using microcontroller that according to the datasheet, has a Flash memory that can be reprogrammed a minimum of ...
6k views

### Can the multiple linear correlation coefficient be negative?

I am using IDL regression function to compute the multiple linear correlation coefficient... ...
260 views

### Statement of result for binomial confidence intervals

Confidence intervals for binomial proportions have irregular coverage over the range of possible population parameters (e.g. see Brown et al. 2001 ...
1k views

### Readable introduction to measure theory

I'm interested in learning more about nonparametric Bayesian (and related) techniques. My background is in computer science and though I have never taken a course on measure theory or probability ...
184 views

### Suitable Distribution/Methodology for Estimating Data Points

I am trying to model future sales data for products which have very low sales volume. I am a programmer with a smattering in statistics, so I apologise in advance if this qustion is naive! My ...
679 views

### Group vs Stacked Bar Plots

What are the appropriate uses for a grouped vs a stacked bar plot?
185 views

### How to model pairwise preference with both strong and weak preferences?

I have large comparison data in form In a pairwise comparison data each data point compares two alternatives. For instance: A > B (A is preferred to B, A and B are classes, not numbers) A > B B > A ...
2k views

### What is the prediction error while using deming regression (weighted total least squares)

Deming Regression is a regression technique taking into account uncertainty in both the explanatory and dependent variable. Although I have found some interesting references on the calculation of ...
343 views

### Low-pass Filter

I collected some data with an instruments with 1Hz sampling clock, now I want to low-pass filter the data to separate the mean and fluctuation part (Reynolds decomposition). How can I design a ...
10k views

### Graph theory — analysis and visualization

I am not sure the subject enters into the CrossValidated interest. You'll tell me. I have to study a graph (from the graph theory) ie. I have a certain number of dots that are connected. I have a ...
536 views

### Proc Calis (or TCalis) and p-values

Anyone know why when you run a SEM model in SAS using proc calis (or tcalis) you do not get p-values for the parameter estimates? It does supply a t-value however. Two popular SEM packages in R, ...
2k views

### Time series cross section forecasting with R

I have a (I suspect) simple question. I have time series cross section data on voting behaviour in the Council of the European Union (the monthly number of yes, no and abstentions for each member ...
1k views

### Analysing questionnaire data

I want to test if there is a rivalry among two siblings in a family. I have 15 questions in my study and I let my 100 respondents ( distributed equally to two siblings) ranked them 1 to 15. How ...
304 views

### Is visualization sufficient rationale for transforming data?

Problem I would like to plot the variance explained by each of 30 parameters, for example as a barplot with a different bar for each parameter, and variance on the y axis: However, the variances ...
296 views

### How to calculate probability for a multivariate/continuous event

I'm brushing up my stats for an AI course that is going to show me the Gaussian mixture model. My prof said I'm supposed to know how to "calculate the probability of a multivariate and continuous ...
689 views

### What is the conjugate of the noncentral hypergeometric distribution?

I want to find the conjugate prior distribution for the Fisher's noncentral hypergeometric distribution? Basically I want to integrate the parameters out of the distributions to arrive at the Bayesian ...
2k views

### How to calculate the rowMeans with some single rows in data?

I tried to group a set of elements and to calculate the row means If my list has more than one element, it works fine: ...
3k views

### Why do I get different heteroscedasticity robust standard errors in R when using the plm package?

I am now writing my bachelors thesis and I have come across some difficulties. I am about to do some panel regressions with time and entity fixed effects and I would therefore like to use the plm ...
630 views

### Which method to use for anomaly detection?

I think people here could guide me in solving a problem related to anomaly detection in Computer Science. The term anomaly here refers to some undesired event occuring in the system like a virus ...
12k views

### Which permutation test implementation in R to use instead of t-tests (paired and non-paired)?

I have data from an experiment that I analyzed using t-tests. The dependent variable is interval scaled and the data are either unpaired (i.e., 2 groups) or paired (i.e., within-subjects). E.g. ...
292 views

### Is it possible to weight survey observations to more than one distribution?

I have a sample survey of a population whose distributions of certain characteristics are not identical to the distributions of the overall population. For example, the age of my respondents may be ...
1k views

### Is a correlation analysis with Pearson's correlation and Bonferroni Method a valid approach to find correlations between two sets of data

I'm studying Biomedical Computer science and I have to research a paper about genotype-phenotype association. In this paper the authors use a correlation analysis by first calculating the Pearson ...
956 views

### Simple and multiple logistic regression

I have almost two questions. I need a single covariate logistic regression (LR) for each of my variables. Should I do it manually in SPSS, selecting each variable and do logistic regression? Is there ...
1k views

### Is principal components analysis valid if the distribution(s) are Zipf like? What would be similar to PCA but suited to non gaussian data?

I'm analyzing people based on their twitter stream. We are using a 'word bag' model of users, which basically amounts to counting how often each word appears in a persons twitter stream (and then ...
392 views

### The probability for two people to provide identical answers on survey questions

Here is the problem: A survey contains 7 binary questions (Yes/No responses). If two people are answering the survey, what is the probability for their answers on 4 or more of the questions to match? ...
469 views

### Is there a SoftMax distribution with confidence parameters?

This is a softmax probability distribution: $$P(i| w_1, w_2, \ldots, w_n) = \frac{exp(w_i)}{\sum_{i=1}^n exp(w_i)}.$$ It known also as Boltzmann distribution. It is used in generalized Bradley-Terry ...
377 views

### Confidence interval for success probability in negative binomial experiment

Suppose I have a biased coin (heads with probability p), and I keep flipping it until I get t tails. So I had to flip n times in total to get t tails. How do I find a (frequentist) confidence interval ...
5k views

### Proving that the squares of normal rv's is Chi-square distributed

I start with three independent random variables, $X_1, X_2, X_3$. They are each normally distributed with: $$X_i \sim N(\mu_i, \sigma^2), i = 1, 2, 3.$$ I then have three transformations, ...
695 views

### Why are my constraints getting dropped?

I'm currently applying the Roy Zelner test of poolability as shown in the excellent article of Andrea Vaona, in fact I'm working with panel N=17 T=5, and my model looks like this : Y_{it}= ...
370 views

### Queueing Theory: How to estimate steady-state queue length for single queue, N servers?

I have a real-life situation that can be solved using Queueing Theory. This should be easy for someone in the field. Any pointers would be appreciated. Scenario: There is a single Queue and N ...
125 views

### Predicting a semi-deterministic process

Say I have a process that gives me 3 outputs: $O^1$, $O^2$ and $O^3$. The outputs are generated from a semi-deterministic process, i.e. there is a deterministic component in the outputs, along with a ...
192 views

### Correct way to calibrate means

I'm working on benchmarking the speed of various JavaScript methods. Part of the benchmark process requires repeating a test for a minimum time (to reduce the percentage uncertainty to at or less than ...
1k views

### Good book on statistics [duplicate]

Possible Duplicate: What book would you recommend for non-statisticians? Hello all, Which is a good book for self-learning of statistics? I tried the "Head first statistics" which starts ...
102 views

### Use install.packages() to build and install all available architectures by default? [closed]

Is there a way to use install.packages() so that it will build and install both 32-bit and 64-bit versions of a package from source by default? I have multiple ...
161 views

### Good way to rank/sort data that falls in the lower range

I have a bunch of data like this: P1 [1, 2, 3, 4, 5, 6, 7, 8, 10] P2 [5, 8, 10, 12, 20] P3 [10, 201, 440] P4 [1, 2, 10] P5 [1, 2] Right now it's ranked by the ...
3k views

### Testing the normality assumption for repeated measures anova? (in R)

So assuming that there is a point in testing the normality assumption for anova (see 1 and 2) How can it be tested in R? I would expect to do something like: ...
459 views

### Zero-truncated Sichel distribution in R

I'm trying to fit the GAMLSS library's Sichel distribution to some zero-truncated data, but the only way to get the function to work is to include the zero-class anyway but give it a frequency of 0, ...
3k views

### R-squared result in linear regression and “unexplained variance”

I did a linear regression in R and got the following result: ...
377 views

### Expected values for chi-squared test on binned paired counts

I want to do a chi-squared test on data that looks like this: A B 0 0 1 0 0 1 1 1 8 0 3 4 ... You can think of each pair as one trial with two participants. In ...
1k views

### Interpretation of log likelihood and covariate significance in Cox regression

Another newbie question here (probably piece of cake for you guys). When I run a Cox Regression and one of my covariates come out as significant: ...
629 views

### How to handle age at measure-start in Cox regression?

I'm a statistics newbie (medical student) trying my luck with a Cox regression for a survival analysis on the outcome of a specific type of operation. And I'm trying to determine which variables to ...
7k views

### Akinator.com and Naive Bayes classifier

Context: I am a programmer with some (half-forgotten) experience in statistics from uni courses. Recently I stumbled upon http://akinator.com and spent some time trying to make it fail. And who ...
726 views

### Classical measurement error model in R

I'm not sure if this is precisely a measurement error model or not. I'm working on performing meta analysis, and the model I'm starting with is fairly basic. \begin{aligned} X_i &= \mu_i + e_i ...
13k views

### Does an unbalanced sample matter when doing logistic regression?

Okay, so I think I have a decent enough sample, taking into account the 20:1 rule of thumb: a fairly large sample (N=374) for a total of 7 candidate predictor variables. My problem is the following: ...
513 views

### Discrepancy between stepwise and nominal logistic regression results in JMP

I have carried out a stepwise logistic regression in JMP. Then (using the proper button in the program window), I have chosen to build a nominal logistic regression model using (only) the variables ...
3k views

### Evaluating effect sizes of interactions in multiple regression

I have been running 3-level multilevel models with HLM, and my main interest is in some cross-level interaction effects that I am finding. My concern is that the effect sizes of these interactions ...
109 views

### Need good material on multifractal analysis [closed]

I'm searching for some good reading material on multifractal analysis. Preferably something accessible that doesn't put the stress too much on mathematical proofs but rather on applications. As long ...