ancova anova binomial chi-square chi square clustering coefficient confidence interval confidence intervals correlation data distribution effect size error factor analysis fixed effects glm help needed help please hypothesis testing interaction interpretation likert likert scale linear regression logistic regression logit loop manova means multicollinearity multiple regression multivariate non-parametric normal normal distribution normality p-value package panel data prediction probability psychology p value r-lang regresion regression regression analysis repeated measures repeated measures anova residuals sample size sas sem significance simulation spss standard deviation standard error stata statistic statistical analysis statistics stats survival analysis t-test test time series variables variance