Question

1. on a race track, you take a random sample of the speed of 40 cars and determine that their average speed is 94 mph. which statement is true?

a. you conclude that the average speed of all the cars is close to 94 mph.
b. you conclude that the speed of all cars on this track is exactly 94 mph.
c. you conclude that the average speed of all cars on this track is close to 94 mph.
d. you conclude that the speed of more than half of the cars on this track is more than 94 mph.

Explanation:

Step1: Understand sampling concept

A sample is used to estimate population - parameters. Here, the sample of 40 cars' speeds is used to estimate the average speed of all cars on the track.

Step2: Analyze each option

• Option a: "all the cars" is too general, not just cars on the track.
• Option b: A sample average doesn't mean the population value is exactly the same. There is sampling - error.
• Option c: A sample average of 40 cars' speeds can be used to estimate that the average speed of all cars on this track is close to 94 mph. This is correct as sampling is used for such estimations.
• Option d: The sample average doesn't give information about the proportion of cars above or below the sample average in the population.

Answer:

c. You conclude that the average speed of all cars on this track is close to 94 mph.