Question

In a debate on altering the traffic system in the city centre, measurement of a number of cars per minutes were taken at two intersections during the hours between 07h00 and 08h00 (when the roads were most busy). The results are shown in the table below:

Number of cars	frequency
10-14	5
15-19	8
20-24	10
25-29	12
30-34	14
35-39	5
40-44	3
45-48	3

1. Average
2. Median and the mode
3. Standard deviation
4. Interquartile range
5. Co-efficient of variation

Answer 1

Descriptive Statistics

First we construct the following table:

Class limits	Class boundaries	x	f	xf	x2f	cumulative freq
10-14	9.5-14.5	12	5	60	720	5
15-19	14.5-19.5	17	8	136	2312	13
20-24	19.5-24.5	22	10	220	4840	23
25-29	24.5-29.5	27	12	324	8748	35
30-34	29.5-34.5	32	14	448	14336	49
35-39	34.5-39.5	37	5	185	6845	54
40-44	39.5-44.5	42	3	126	5292	57
45-48	44.5-49.5	47	3	141	6627	60
Total			60	1640	49720