The distribution of speeds on a particular highway has a mean of 60 mph with a standard deviation of 10 mph. The distribution of speeds is NOT known to be bell-shaped. Use the scenario to answer the next 3 questions. At least what percentage of cars is traveling between 40 and 80 mph?

At least what percentage of cars is traveling between 20 and 100 mph?

If a sample of 40 cars is selected at random, estimate the number of cars that are traveling between 40 and 80 mph.

a) At least what percentage of cars is traveling between 40 and 80 mph?

75%

b) At least what percentage of cars is traveling between 20 and 100 mph?

93.75%

c) If a sample of 40 cars is selected at random, estimate the number of cars that are traveling between 40 and 80 mph.

30 cars.

Step-by-step explanation:

We apply Chebyshev's Theorem

This states that:

1) At least 3/4 (75%) of data falls within 2 standard deviations from the mean - between μ – 2σ and μ + 2σ.

2) At least 8/9 (88.89%) of data falls within 3 standard deviations from the mean - between μ - 3σ and μ + 3σ.

3) At least 15/16 (93.75%) of data falls within 4 standard deviations from the mean - between μ - 4σ and μ + 4σ.

From the question, we have:

Mean of 60 mph

Standard deviation of 10 mph.

a) At least what percentage of cars is traveling between 40 and 80 mph?

Applying:

Applying the first rule: At least 3/4 (75%) of data falls within 2 standard deviations from the mean - between μ – 2σ and μ + 2σ.

μ – 2σ

60 - 2(10)

60 - 20

= 40 mph

μ + 2σ.

60 + 2(10)

60 + 20

= 80 mph

Hence, at least 75% of cars is traveling between 40 and 80 mph.

b) At least what percentage of cars is traveling between 20 and 100 mph?

At least 15/6 (93.75%) of data falls within 4 standard deviations from the mean - between μ – 4σ and μ + 4σ.

μ – 4σ

60 - 4(10)

60 - 40

= 20 mph

μ + 4σ.

60 + 4(10)

60 + 40

= 100 mph

Hence, at least 93.75% of cars is traveling between 40 and 80 mph.

c) If a sample of 40 cars is selected at random, estimate the number of cars that are traveling between 40 and 80 mph.

Since we know from question a) that

at least 75% of cars is traveling between 40 and 80 mph.

Given a sample of 40 cars:

75% of 40 cars

= 75/100 × 40

= 30 cars.

The number of cars that are traveling between 40 and 80 mph is 30 cars.

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