/*
UMD ECON-626 FALL 2019
Power, PART 2: multiple periods (the case for more T)
*/
set more off
// consider typing "help sampsi"
// 2.1.
// we have a guess about the mean among CONTROL = 0
// we have a guess about the mean among TREATMENT = 0.5
// we have a guess about the SD of the outcome = 1
// we want to have enough observations for power = 0.80
// what sample size is needed? use the sampsi command.
// 2.2.
// to these four options, add:
// pre(1) post(1) r1(0) r01(0)
// meaning
// one pre-treatment observation per unit
// one post-treatment observation per unit
// zero correlation from pre to post
// zero correlation among post treatment observations
// nothing changes for two methods, but a change for one method. why?
// 2.3.
// now change the correlations (r1 and r01) which had been set to zero:
// first so they are both 0.2,
// then so they are both 0.4,
// then so they are both 0.6. What happens?
// 2.4.
// now with each of those correlations,
// try setting the number of "pre" observations to zero,
// and the number of "post" observations to 2.
// What changes? Why?