Question

A student researcher compares the heights of American students and non-American students from the student body of a certain college in order to estimate the difference in their mean heights. A random sample of 12 American students had a mean height of 69 inches with a standard deviation of 2.57 inches. A random sample of 17 non-American students had a mean height of 64.8 inches with a standard deviation of 2.12 inches. Determine the 90% confidence interval for the true mean difference between the mean height of the American students and the mean height of the non-American students. Assume that the population variances are equal and that the two populations are normally distributed.

Step 1 of 3: Find the point estimate that should be used in constructing the confidence interval.

Step 2 of 3: Find the margin of error to be used in constructing the confidence interval. Round your answer to six decimal places.

Step 3 of 3: Construct the 90% confidence interval. Round your answers to two decimal places. (lower and upper endpoints)

Answer 1

1)

point estimate =x1-x2 =4.2

2)

for 90 % CI & 27 df value of t=			1.703
margin of error E=t*std error =			1.485755

(please try 1.486007 if above comes wrong)

3)

lower bound=mean difference-E=			2.71
Upper bound=mean differnce +E=			5.69