# All Questions

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### Significant multiple linear regression model with non-significant betas?

In multiple linear regression, let us say that the F test shows that the model is significant. But the t-tests for beta values does not say that the beta values are non-zero. What can we conclude in ...
28k views

### Interpretation of log transformed predictors in logistic regression

One of the predictors in my logistic model has been log transformed. How do you interpret the estimated coefficient of the log transformed predictor and how do you calculate the impact of that ...
206 views

7k views

### Confidence interval for geometric mean

As title, is there anything like this? I know how to calculate CI for arithmetic mean, but how about geometric mean? Thanks.
44k views

### How to do logistic regression subset selection?

I am fitting a binomial family glm in R, and I have a whole troupe of explanatory variables, and I need to find the best (R-squared as a measure is fine). Short of writing a script to loop through ...
2k views

### Correlation analysis and correcting $p$-values for multiple testing

I am investigating the effect of a drug on EEG and cognition in epilepsy patients. We have done EEG and neuropsychological (NP) tests twice, before and after medical treatment. Some of parameters in ...
115 views

### Relationship between MDL and “difficulty of learning from data”

While trying to make sense of MDL and stochastic complexity, I found this previous question: Measures of model complexity, in which Yaroslav Bulatov defines model complexity as "how hard it is to ...
1k views

### Looking for stats/probability practice problems with data and solutions

I am looking for a self-study site on the web that will allow me to verify my understanding of some basic probability and stats concepts and operations. What I would like is a site with data and ...
3k views

### No lrtest() function available in lmtest

I have got a strange problem with using functions which are supposed to be in the libraries lmtest & language R (downloaded from cran.r-project recently), namely lrtest() and pvals.fnc() - however,...
4k views

### Clustered standard errors and multi-level models

Stata allows estimating clustered standard errors in models with fixed effects but not in models random effects? Why is this? By clustered standard errors, I mean clustering as done by stata's ...
4k views

### How should I measure the relationship between a variable containing text and a binomial variable?

I have data in this format: Words,Source,Result pestology Gomel, cheap, 0 cocreating, cheap, 1 munitioner impersonating nonextinct, cheap, 1 Kolomna, expensive, 1 Enyo's snakemouth, expensive, 0 ...
109 views

### Indicators of disease

I have this dataset with size (rows) and shape (columns) and in each cell #disease/#in cell . How would I answer the following questions? Is size an indicator of disease? Is shape an indicator of ...
6k views

### Normalizing data between 0 and 1

I am a novice when it comes to stats, so I apologize beforehand for the simplicity of my question. I trying to figure out the best way to normalize (this may be the wrong term) my data in so that the ...
311 views

### What is the right name for the variant of the Kolmogorov-Smirnov statistic that retains the sign of the difference?

The two-sample Kolmogorov-Smirnov statistic is normally defined as $D = \max_x |A(x) - B(x)|.$ I would like to compute a variant that retains the sign of the difference between the distribution ...
158 views

### How to assess drug effects using annual death rate data?

I am planning a study to collect data of patients dying after brain infection versus number of cases for the next 5 years in 2 cities where they manage the disease with different drugs. Will a year ...
672 views

### Fitting 4-moment distribution with mixture gaussian

I know that Mclust does the fit on its own but I am trying to implement an optimization with the aim to generate a mixture of 2 gaussians with the combine moments as closed as possible to the moment ...
488 views

### Help with deploying a model

The two main packages I use at work are Palisade Risk and SPSS Clementine - they are both quite old versions and I've been supplementing the ability to analyze properly at work with more modern ...
8k views

### What is the probability that a normal distribution with infinite variance has a value greater than its mean?

I got asked something similar to this in interview today. The interviewer wanted to know what is the probability that an at-the-money option will end up in-the-money when volatility tends to infinity....
9k views

### How to set up a two-way mixed ANOVA with a covariate in SPSS?

I wanted to carry out a two-way ANCOVA for my data. However, SPSS isn't liking that I have only one IV. I have One IV: Group (3 levels, i.e. 2 experimental groups and a control group), One DV: ...
40k views

### Help on subsetting data frames using multiple logical operators in R

In R, I am trying to write a function to subset and exclude observations in a data frame based on three variables. My data looks something like this: ...
6k views

### Advice on classifier input correlation

I have a lot of data on previous race history and I'm trying to predict a percentage chance of winning the next race using Regression, kNN, and SVM learning algorithms. Say a race has 5 runners, and ...
2k views

### Is the matrix dimension important for performing a valid PCA?

If $X$ is a $m × n$ matrix, where $m$ is the number of measurement types (variables) and $n$ is the number of samples, would it be correct to perform a PCA on a matrix that has $m \geq n$ ? If ...
385 views

### Detecting reflection in non-orthogonal rotation

I've known that, in orthogonal rotation, if the rotation matrix has determinant of -1 then reflection is present. Otherwise the determinant is +1 and we have pure rotation. May I extend this "sign-of-...
9k views

### Choose factor level as dummy base in lm() in R

Lets say I am regressing Y on X1 and X2, where X1 is a numeric variable and X2 is a factor with four levels (A:D). Is there any way to write the linear regression function ...
5k views

### The use of median polish for feature selection

In a paper I was reading recently I came across the following bit in their data analysis section: The data table was then split into tissues and cell lines, and the two subtables were separately ...
525 views

### Using QDA for Non-Gaussian distributions

I am evaluating a Quadratic Discriminant Analysis (QDA) classifier on a high-dimensionality feature set. The features come from highly non-Gaussian distributions. However, when I transform the ...
3k views

481 views

### Introductory statistics video courses for social scientists

I have just discovered, through this answer, a nice video resource to share with students in introductory statistics courses. The lectures, produced by the Khan Academy, are fairly didactic and well ...
11k views

### Logic behind the ANOVA F-test in simple linear regression

I'm trying to understand the logic behind the ANOVA F-test in Simple Linear Regression Analysis. The question I have is like follows. When the F value, i.e. MSR/MSE...