Answer:
{58.02007 , 61.97993]
Step-by-step 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
[tex]= [60 - \frac{1.97993 \times 11}{\sqrt{121} }] , [60 + \frac{1.97993 \times 11}{\sqrt{121} }][/tex]
= {58.02007 , 61.97993]
Basically we applied the above formula to determine the confidence interval