You are constructing a confidence interval for scores on a standardized test. The test is designed with a population standard deviation of 15. You find an average test score of 81 in a sample of 125 eight-graders. What approach is most appropriate to calculate the confidence interval? O CI = X+Zox O CI = Xttsx O CI =P+25p Not this answer QUESTION 38 2. You want to calculate a 95% confidence interval using the equation CI =X + ZOx. What z-value should be used for this interval? QUESTION 39 2.5 You want to calculate a 90% confidence interval using the equation CI =X + tSx. Your sample size is 20. What t-value should be used for this interval? QUESTION 40 2.5 po You want to calculate a 85% confidence interval using the equation CI =X +Zox. What z-value should be used for this interval? Click Save and Submit to save and submit. Click Save All Answers to save all answers