The Highway Safety Department wants to study the driving habits of individuals. A sample of 41 cars traveling on the highway revealed an average speed of 60 miles per hour and a standard deviation of 7 miles per hour. The population of car speeds is approximately normally distributed. Determine a 90% confidence interval estimate for the speed of all cars.

58,21    ≤   μ  ≤   61,79

Step-by-step explanation:

Normal Distribution

Poputation size        n = 41

Population mean         X  = 60

Population standard deviation    σ = 7

Question is: Confidence Interval 90 % ??

As Confidence Interval is 90 %   then  α  = 10 %

And as we are dealing with a two tail test

α/2  = 0,05

We look in Z table for values for  α/2  = 0,05  and find

z(α/2)  =  - 1,64      and    z(α/2) =  1,64

Then

Confidence Interval is

X - Zα/2 * σ/√n   ≤  μ  ≤  X + Zα/2 * σ/√n

60 - ( 1,64 ) * 7/√41  ≤   μ  ≤  60 + ( 1,64 ) * 7/√41

60 -  1,64 * 1,09375   ≤   μ  ≤  60 +  1,64 * 1,09375

60 - 1,79375    ≤   μ  ≤  60 +  1,79375

58,21    ≤   μ  ≤   61,79

where is the page?

step-by-step explanation:

c.

step-by-step explanation:

because first you have to add the 4x, 9x, and the 7x together and you get 20x and then you add the last numbers up and you get 5and then you put the subtraction sign in there and that's how you get the answer.