# Thread: How do you do a confidence interval for this problem?

1. ## How do you do a confidence interval for this problem?

Hallam, Price, and Katsarou investigated the influence of background noise on classroom performance for children aged 10 to 12. In one part of the study, calming music led to better performance on an arithmetic task compared to a no-music condition. Suppose that a researcher selects one class of n=18 students who listen to calming music each day while working on arithmetic problems. A second class of n=18 serves as a control group with no music. Accuracy scores are measured for each child and the average for students in the music condition is M=86.4 with SS=1550 compared to an average of M=78.8 with SS=1204 for students in the no-music condition.

I have to compute the 90% confidence interval for the population mean difference

I figured the point estimate is 7.6, but I'm confused where to go from there

2. ## Re: How do you do a confidence interval for this problem?

looks like a basic 2 sample t test
BUT we need to know if you are assuming that the population variances
of the two groups are equal
which I would agree to

$\bar X_1-\bar X_2\pm t_{n_1+n_2-2,.05}S_p\sqrt{{1\over n_1}+{1\over n_2}}$