/************
syntax 11.2
************/
/*************************************************************
Power Analysis: sampsi -- Sample size and power determination
*************************************************************/

/***Example 1: one-sample test of proportion***/
sampsi .5 .35, power(.8) onesample		/*the default alpha is .05*/
sampsi .5 .35,n(20) onesample

/***Example 2: two-sample test of proportion***/
sampsi .3 .2, alpha(.05) power(.8)
sampsi .3 .2,n1(300) n2(250) alpha(.01)

/***Example 3: one-sample test of mean***/
sampsi 0 -10,sd(6) a(.01) onesided p(.95) onesample
sampsi 0 -10,sd(6) a(.01) onesided n(10) onesample

/***Example 4: two-sample test of mean***/
sysuse auto,clear
bysort foreign:sum weight
sampsi 2300 3300,sd1(430) sd2(700) r(2) p(.99)
sampsi 2300 3300,sd1(430) sd2(700) n1(10) n2(10)

/***chi-square test of independence***/
sysuse auto,clear
gen mpg1=mpg>21.3
tab mpg1 foreign,chi2

/******
ANOVA
******/
/***one-way ANOVA***/
sysuse auto,clear
oneway mpg foreign
anova mpg foreign
anova mpg foreign price weight
anova mpg foreign price weight,cont(price weight)
anova mpg foreign price weight,cont(price weight) reg
reg mpg foreign price weight

/***How to plot ANOVA cell means in Stata***/
use http://www.ats.ucla.edu/stat/stata/faq/crf24,clear
anova y a b a*b
predict yhat
sort a b
graph twoway scatter yhat b, connect(L)	/***or***/
net install gr0009.pkg
anovaplot b a
anovaplot b a,scatter(msym(i)) 	/***use option "scatter(ms(i))" to suppress plotting of response data***/

/***How to do ANOVA contrasts in Stata?***/
net install anovacontrast.pkg
sysuse auto,clear
keep if rep78>2&rep78<.		/***anovacontrast gives incorrect and misleading results if there are missing or empty cells***/
anova mpg rep78
table rep78,contents(mean mpg)
anovacontrast rep78, values(-1 0 1)		/***group 1 versus group 3***values(numlist) specifies the weights for the contrast and is not optional***/
anovacontrast rep78, values(0 -1 1)		/***group 2 versus group 3***/
anovacontrast rep78, values(-1 1 0)		/***group 1 versus group 2***/