Question

The Highway Safety Department wants to study the driving habits of individuals. A sample of 121 cars traveling on the highway revealed an average speed of 60 miles per hour with a standard deviation of 11 miles per hour. Determine a 95% confidence interval estimate for the speed of all cars.

Answer 1

{58.02007 , 61.97993]

Explanation:

Data are given in the question

Sample of cars = n = 121

Average speed = sample mean = 60

Standard deviation = sd = 11

And we assume

95% confidence t-score = 1.97993

Therefore

Confidence interval is

`= [60 - (1.97993 * 11)/(√(121) )] , [60 + (1.97993 * 11)/(√(121) )]`

= {58.02007 , 61.97993]

Basically we applied the above formula to determine the confidence interval