Question in statistics, what does df denote? if a simple random sample of 2424 speeds of cars on california highway 405 is to be used to test the claim that the sample values are from a population with a mean greater than the posted speed limit of 65 mi/h, what is the specific value of df?

N = 2424 is the sample size (amount of cars being sampled)
df = degrees of freedom
df = n-1
df = 2424-1
df = 2423

Side Note: if there is a typo and the sample size should be n = 24 (instead of 2424), then the df would be df = n-1=24-1 = 23

D, 161.16 square centimeters.

Step-by-step explanation:

The surface area of a cylinder (shape of each steel rod) is given by this formula:

, where the first 2*pi*r*h measures the area of the curved surface while the second 2*pi*r^2 measures the area of the two circles on the top and bottom.

We are given the area of the top of one rod, which is 7.07 square centimeters.

We are also given the area of the body of one rod, which is 39.58 square centimeters.

The top of one rod is the shape of a circle, and we know there are two circles on both sides of a cylinder, so the surface area of both circular sides are 7.07.

The total surface area of a cylinder is the body plus both circular ends, so the surface area for this cylinder is:

39.58 + 7.07 + 7.07 = 53.72

There are three cylinders, so multiply this value by three to get the answer, 161.16 square centimeters.