It is advertised that the average braking distance for a small car traveling at

Question

It is advertised that the average braking distance for a small car traveling at 65 miles per hour equals 120 feet. A transportation researcher wants to determine if the statement made in the advertisement is false. She randomly test drives 36 small cars at 65 miles per hour and records the braking distance. The sample average braking distance is computed as 114 feet. Assume that the population standard deviation is 22 feet.

Calculate the value of the test statistic and the p-value. (Negative values should be indicated by a minus sign. Round "Test statistics" to 2 decimal places and "p-value" to 3 decimal places.)

Repeat the test with the critical value approach. (Negative values should be indicated by a minus sign. Round your answers to 2 decimal places.)

It is advertised that the average braking distance for a small car traveling at 65 miles per hour equals 120 feet. A transportation researcher wants to determine if the statement made in the advertisement is false. She randomly test drives 36 small cars at 65 miles per hour and records the braking distance. The sample average braking distance is computed as 114 feet. Assume that the population standard deviation is 22 feet.

Explanation / Answer

H0: mu = 120 ft

Ha: mu not equal to 120 ft

Two tailed test at 0.01

x bar =114 and sigma = 22

n =36

std error = 22/rt n = 3.667

Test statistic = Mean diff/3.667 = -6/3.667 = -1.64

df = 35

p value = .109964.

The result is not significant at p < .01.

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