This week's topics covered running an independent samples t-test and interpreting using R.
Question # 1 : Find your two sample means.
> x <- c(9,8,3,8,10) > y <- c(3,1,2,6,4,3,6) > tTest <- t.test(x,y) > tTest$estimate mean of x mean of y 7.600000 3.571429
Question # 2 : Find the degrees of freedom(s).
> tTest$parameter df 6.768656
Question # 3 : Find t-test statistic score (s).
> tTest$statistic t 2.865148
Question # 4 : Find the P value(s).
> tTest$p.value  0.02505219
Question # 5 : Assume you had chosen an alpha value of .05., Would this result have been statistically significant?
Yes. The p-value is <= 0.05.
Question # 6 : What critical value would your obtained t-test value have to exceed to be significant at the .01 level (assume a two-tailed test)?
> z <- qnorm(0.99 + (0.01 / 2)) > p <- pnorm(z) > z  2.575829 > p  0.995 For the t-test to exceed the significance value of 0.01, z must be 2.576 or p must be 0.995