A survey of several 8 to 10 year olds recorded the following amounts spent on a trip to the mall: $24.95, $20.44, $20.63, $21.78 Construct the 99% confidence interval for the average amount spent by 8 to 10 year olds on a trip to the mall. Assume the population is approximately normal. Copy Data Step 3 of 4: Find the critical value that should be used in constructing the confidence interval. Round your answer to three decimal places.