Short answer questions: Please state True or False along with an explanation.

1. One can estimate a within-effect of a non-time-varying covariate on outcomes.
2. One can estimate both within and between effects on time-varying covariates.
3. The difference between running a regular OLS regression (usingregress) versus a population average model (usingstrong, pa) on longitudinal data is in the assumption about the correlations in the outcome data.
4. The coefficient on a time-varying covariate in a random-effects linear model represents within-effects.
5. The coefficient on a time-varying covariate in a fixed effect linear model represents between-effects.
6. It is possible to estimate both within and between effects on time-varying covariates in a random effects linear model.