Question

a.In a survey, 21 people were asked how much they spent on their child's last birthday gift. The results were roughly bell-shaped with a mean of $40 and standard deviation of $9. Construct a confidence interval at a 80% confidence level. Give your answers to one decimal place.

b. If n=30, ¯x¯(x-bar)=48, and s=9, find the margin of error at a 80% confidence level

Give your answer to two decimal places.

c. In a survey, 22 people were asked how much they spent on their child's last birthday gift. The results were roughly bell-shaped with a mean of $39 and standard deviation of $7. Find the margin of error at a 98% confidence level.

Give your answer to two decimal places.

d. You intend to estimate a population mean μμ with the following sample.

76.4

41.1

37.7

59.6

66.6

95.3

64

52.5

54.1

66.7

68.6

You believe the population is normally distributed. Find the 90% confidence interval. Enter your answer as an open-interval (i.e., parentheses) accurate to twp decimal places (because the sample data are reported accurate to one decimal place).

90% C.I. =

Answer should be obtained without any preliminary rounding. However, the critical value may be rounded to 3 decimal places.

Answer 1