== Questions about distributions of random variables ==

 1. [[FAQ/normN|How many observations do I need to make z-scoring (assuming Normality) feasible?]]

 1. [[FAQ/stables | Are there any on-line statistical tables for commonly used distributions?]]

 1. [[FAQ/Sattherthwaite|Why are the degrees of freedom not whole numbers?]]

 1. [[FAQ/ztcF|What is the relationship between the z, t, chi-square and F distributions?]]

 1. [[attachment:asymmetry.pdf|A Normalising transformation of ratios of form (L-R)/(L+R)]] 

 1. [[FAQ/Combinatorics|What is the probability of a repetition in a sequence of size k taken from K stimuli?]]

 1. [[FAQ/multi|How do I evaluate Multinomial probabilities of pooled trial frequencies of locations of peaks which can occur in one of K positions in each trial?]]

 1. [[FAQ/wblfit|How do I fit a Weibull distribution to scores over time using MATLAB and notes on using non-linear least squares?]]

 1. [[FAQ/recode|How do I recode levels of a group variable in SPSS?]]

 1. [[FAQ/itt|What is an intention to treat analysis?]]

 1. [[FAQ/aster|How do I evaluate a number to a general power in SPSS?]]

 1. [[FAQ/cis|A note on comparing confidence intervals and statistical significance]]
 
 1. [[FAQ/poolse|How do I obtain a pooled standard error of the mean?]]

 1. [[FAQ/semsd|How do I obtain the standard deviation from the standard error of the mean (s.e.m.) and how does this and the mean vary with sample size?]]

 1. [[FAQ/FVars| What is the variance of the mean of my transformed data and the variance of combinations of means?]]

 1. [[FAQ/wttest| How do I do a t-test between two weighted means?]] 

 1. [[FAQ/meanmed|What is the relationship between the mean and the median from a sample and how do I compute 95% CIs for the median?]]

 1. [[FAQ/thirds|What is an optimal cut-off for the discretization/splitting of a continuous variable and how do we use this in a regression?]]

 1. [[FAQ/eorder| A quick approximation for Normally distributed expected order statistics]]

 1. [[FAQ/zpercs| How do I convert a z-score into a percentile in SPSS?]]

 1. [[FAQ/subscale| How do I derive an expected total for a subset of items based on the expected overall total?]] 

 1. [[FAQ/absdiff| How do I compute a difference in errors adjusted for overall number of errors when the errors have different signs?]] 

 1. [[FAQ/ResidualsNonNormality|Residuals and (Non-)Normality]]

 1. [[FAQ/ResidsRepMeas|How do I check Normality assumptions in repeated measures analyses in SPSS?]]

 1. [[FAQ/Simon|Testing normality including rules of thumb for skew, kurtosis in SPSS]]

 1. [[FAQ/Winsor|Methods of handling outliers.]]

 1. [[FAQ/EXponential| How do I produce truncated exponential random variables using MATLAB?]]

 1. [[FAQ/mixtures| How do I obtain parameter estimates for finite Normal mixture distributions using SPSS and BMDP?]]

 1. [[FAQ/perc| How do I find out how many people have a score above a certain value?]]

 1. [[FAQ/percentile| How do I compute percentile thresholds for exponential data and use in outlier detection?]]

 1. [[FAQ/rand| How do I generate a random sample in EXCEL?]]

 1. [[FAQ/randall| Matching groups and randomized allocation to groups]]

 1. [[FAQ/rtest| Some thoughts on testing for randomness]]

 1. [[FAQ/MeanSum|How do I obtain the mean of several variables, each minus the same constant? (In SPSS)]]

 1. [[FAQ/zscore|How do I compute z-scores in SPSS and what is their relationship to comparing group means?]]

 1. [[FAQ/signt|Why does my t-statistic have a negative sign?]]

 1. [[FAQ/pvals|How do I use cumulative distribution functions to compute p-values in SPSS, EXCEL and R?]]

 1. [[FAQ/surv|How do I adjust for age in comparing survival times in two different groups?]]

 1. [[FAQ/t1t2|What is the relationship between intercept and slope for scores at two time points?]]

 1. [[FAQ/atan|Arctan functions in EXCEL.]]

 1. [[FAQ/cdfs| How do I obtain statistical distributions in MATLAB?]]

 1. [[FAQ/gamma|How do I produce random variables which follow a negative skew distribution?]]

 1. [[FAQ/multinorm| How do I calculate probabilities involving the multivariate normal distribution?]]

 1. [[FAQ/boot| Simulations sampling from data with replacement (bootstrapping)]]
  
 1. [[FAQ/secretS| Bootstrapping without replacement (Secret Santa) in R]]

 1. [[FAQ/mvngen| Generating multivariate data with a required correlation matrix]]

 1. [[FAQ/formulae| How do I obtain the formulae behind statistics outputted by SPSS algorithms?]]