Question

A survey of several 11 to 12 year olds recorded the following amounts spent on a trip to the mall: $18.35, $25.19, $27.45 Construct the 80 % confidence interval for the average amount spent by 1 l to 12 year olds on a trip to the mall. Assume the population is approximately normal. Copy Daa Step 3 of 4: Find the critical value that should be used in constructing the confidence interval. Round your answer to three decimal places Tables Keypad Answer How to enter your answer Previous step answers

Answer 1

Ans:

sample size,n=3

df=3-1=2

confidence level=0.8

alpha=0.2

critical t value=tinv(0.2,2)=1.886

sample mean=23.663

sample standard deviation=4.738

80% confidence interval for mean

=23.663+/-1.886*4.738/sqrt(3)

=23.663+/-5.158

=(18.505, 28.822)