Question

. The Connect Internet service officer takes a sample of 30 subscribers to find out the number of hours

they spent ‘on-line’ in the last month. Here are the results:

6 9 14 15 16 17 18 21 23 24

24 27 28 33 36 37 39 39 40 40

41 43 44 45 47 48 53 57 59 63

(i) Construct a stem-and-leaf plot for the raw data.

(ii) Explain why it is likely that the underlying population of all users may have a symmetric

distribution? Give two reasons.

(iii) Construct a frequency distribution for these data, using 5 classes.

(iv) Construct a histogram and a frequency polygon for the cumulative frequency distribution.

[Verify your answer by MICROSOFT EXCEL

Answer 1

increasing order:

6, 9, 14, 15, 16, 17, 18, 21, 23, 24, 24, 27, 28, 33, 36, 37, 39, 39, 40, 40, 41, 43, 44, 45, 47, 48, 53, 57, 59, 63

i)

stem leaf

0 6 9

1 4 5 6 7 8

2 1 3 4 4 7 8

3 3 6 7 9 9

4 0 0 1 3 4 5 7 8

5 3 7 9

6 3

ii)

A symmetrical distribution occurs when the values of variables appear at regular frequencies and often the mean, median, and mode all occur at the same point.

ii)

iv)