Practice Test 3 ~ Ch 8 - 9 Question 2 of 33 (6 points) 1 Question Attempt: 1 of 1 10 11 Espa 5 6 8 9 = 1. - 2 3 The lifetime of a certain type of battery is known to be normally distributed with standard deviation o=24 hours. A sample of 50 batteries had a mean lifetime of 120.1 hours. It is desired to construct a 95% confidence interval for the mean lifetime for this type of battery. Part: 0 / 6 Part 1 of 6 (a) What is the point estimate? The point estimate is |120.1 . X Part: 1 / 6 Part 2 of 6 (b) Find the critical value. The critical value is 1.96. X Part: 2 / 6 Part 3 of 6 (c) Find the standard error. Round to four decimal places. The standard error is |3.3941 X Part: 3 / 6 Part 4 of 6 (d) Find the margin of error. Round to two decimal places. The margin of error is X Next Part Submit