The GPA of accounting students in a university is known to be normally distributed. A random sample of 39 accounting students results in a mean of 2.71 and a standard deviation of 0.15. Construct the 90% confidence interval for the mean GPA of all accounting students at this university.

Scores on the cognitive scale of the bayley-scales of infant and toddler development range from 1 to 19, with a standard deviation of 3. calculate the margin of error in estimating the true mean cognitive scale score, with 99% confidence, if there are 12 infants and toddlers in a sample.