Question

A researcher conducts a mileage economy test involving 90 cars. The frequency distribution describing average miles per gallon (mpg) appears in the following table.

Average mpg	Frequency
15 up to 20	8
20 up to 25	3
25 up to 30	24
30 up to 35	16
35 up to 40	22
40 up to 45	17

a. Construct the corresponding relative frequency, cumulative frequency, and cumulative relative frequency distributions. (Round "Relative Frequency" and "Cumulative Relative Frequency" to 4 decimal places.)

b-1. How many of the cars got less than 35 mpg?

b-2. What percentage of the cars got at least 35 but less than 40 mpg? (Round your answer to 2 decimal places.)

b-3. What percentage of the cars got less than 25 mpg? (Round your answer to 2 decimal places.)

b-4. What percent got 25 mpg or more? (Round your answer to 2 decimal places.)

Answer 1

a) Table for relative frequency, cumulative frequency, and cumulative relative frequency distributions:

Average mpg	Relative frequency	Cumulative frequency	Cumulative relative frequency
15 up to 20	0.0889	8	0.0889
20 up to 25	0.0333	11	0.1222
25 up to 30	0.2667	35	0.3889
30 up to 35	0.1778	51	0.5667
35 up to 40	0.2444	73	0.8111
40 up to 45	0.1889	90	1.0000

b-1) Number of the cars that got less than 35 mpg = 51

b-2) Percentage of the cars that got at least 35 but less than 40 mpg = 24%

b-3) Percentage of the cars that got less than 25 mpg = 12%

b-4) Percent that got 25 mpg or more = 100 - 12 = 88%