From a random sample of 6 students in an introductory finance class that uses? group-learning techniques, the mean examination score was found to be 78.86 and the sample standard deviation was 2.8. 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 74.55 and 8.7?, respectively. Estimate with 90?% confidence the difference between the two population mean? scores; do not assume equal population variances.
The 90?% confidence interval is from a lower limit of __ to an upper limit of ___
?(Round to two decimal places as? needed.)