t-test of differences due to period effect.

#input data g1t1=c(43,41,44,47) g1t2=c(15,19,27,26) g2t1=c(21,25,23,30) g2t2=c(33,39,41,40)

d1=g1t1-g1t2 # differences due to period effect d2=g2t2-g2t1 n1=length(d1) # assume no missing points n2=length(d2) # EQ var t-test of mean diff due to period effect # estimate standard error of period effect se=sqrt((v1*df1+v2*df2)/(df1+df2)*(n1+n2)/(n1*n2)) t=(mean(d1)-mean(d2))/se # observed t-statistic p=pt(t,df1+df2) # test t p=.5-abs(p-.5) # when p > 0.5 then p = 1-p p*2 # 2-tailed P-value

> # EQ var t-test of mean diff due to period effect > p*2 # 2-tailed P-value [1] 0.02433049