Question

The owner of an automobile repair shop studied the waiting times for customers who arrive at the shop for an oil change. The following data with waiting times in minutes were collected over a one-month period.

11	5	4	15
12	4	3	19
10	11	13	15
5	18	6	9
2	4	22	2

(a)

Develop a frequency distribution using classes of 0-4, 5-9, 10-14, 15-19, and 20-24.

Class	Frequency
0-4
5-9
10-14
15-19
20-24
Total

(b)

Develop a relative frequency distribution using the classes in part (a). If required, round your answers to two decimal places.

Class	Relative Frequency
0-4
5-9
10-14
15-19
20-24
Total

(c)

Develop a cumulative frequency distribution using the classes in part (a).

Class	Cumulative Frequency
0-4
5-9
10-14
15-19
20-24

(d)

Develop a cumulative relative frequency distribution using the classes in part (a). If required, round your answers to two decimal places.

Class	Cumulative Relative Frequency
0-4
5-9
10-14
15-19
20-24

(e)

What proportion of customers needing an oil change who wait 9 minutes or less?

Answer 1

The Calculation table for a) , b), c), d)  

Class	Frequency	Rel. Freq	Cumulative. Freq	Cumulative . Rel. Freq
0-4	6	6/20=0.3	6	0.3
5-9	4	4/20 =0.2	6+4 =10	0.3+0.2= 0.5
10-14	5	5/20=0.25	10+5 =15	0.5+0.25 = 0.75
15-19	4	0.2	15+4 =19	0.75+0.2 = 0.95
20-24	1	0.05	19+1 =20	0.95+0.05 = 1
Total	20	1

e) The Proportion of Customers needing oil change who wait 9 minutes or less is 50%

( here just chk the cum. rel freq. col. for class 5-9)