Random Sample

From a random sample of 7 students in an introductory finance class that uses group-learning techniques, the mean examination score was found to be 78.67 and the sample standard deviation was 2.4.

For an independent random sample of 9 students in another introductory finance class that does not use group-learning techniques, the sample mean and standard deviation of exam scores were 71.84 and 8.7, respectively. Estimate with 99% confidence the difference between the two population mean scores; do not assume equal population variances.

The 99% confidence interval is from a lower limit of , to an upper limit of .

(Round to two decimal places as needed.)