95 Confidence Interval Formula T Test. We are 95 confident that the average difference between the pretest and the post test is between 5 9 points and 23 88 points. The confidence interval is 9 2 63.
Alpha required argument this is the significance level used to compute the confidence level. Of the statistic is in the unshaded region confidence intervals ttests p values p 11 31. We could use the t inv function in exce l to calculate this value.
So a significance level of 0 05 is equal to a 95 confidence level.
The sample size n is 30. 20 30 samples have wider confidence intervals signifying greater imprecision. The sample size is n 10 the degrees of freedom df n 1 9. Your desired confidence level is usually one minus the alpha a value you used in your statistical test.
