Question

True or False: A race car driver tested his car for time from 0 to 60 mph, and in 20 tests obtained an average of 4.85 seconds with a standard deviation of 1.47 seconds. A 95% confidence interval for the 0 to 60 time is 4.52 seconds to 5.18 seconds.

Answer 1

False

Explanation:

given that a race car driver tested his car for time from 0 to 60 mph, and in 20 tests obtained an average of 4.85 seconds with a standard deviation of 1.47 seconds.

Sample size n = 20

since population standard deviation is not known, we can use t critical value for finding out the confidence interval

df=19

t critical = 2.045

Margin of error =
`2.045*(s)/(√(n) ) \\=2.045*(1.47)/(√(20) ) \\=0.6722`

conidence interval = Mean±Margin of error

=
`(4.85-0.6722, 4.85+0.6722)\\= (4.1778, 5.5222)`

The given confidence interval is (4.52, 5.18)

Hence the statement is false.