The table gives the distribution of marks of 60 candidates in a test.
Marks
23-25
26-28
29-31
32-34
35-37
38-40
Frequency
3
7
15
21
10
4
(a) Draw a cumulative frequency curve of the distribution. (b) From your curve, estimate the : (i) 80th percentile ; (ii) median ; (iii) semi-interquartile range.
Explanation
Marks
Freq
Class Boundaries
Cum. Freq
23 - 25
3
22.5 - 25.5
3
26 - 28
7
25.5 - 28.5
10
29 - 31
15
28.5 - 31.5
25
32 - 34
21
31.5 - 34.5
46
35 - 37
10
34.5 - 37.5
56
38 - 40
4
37.5 - 40.5
60
(a) (b)(i) 80th percentile = . = 31.5. (ii) Median = (iii) Upper quartile = Lower quartile = Semi-interquartile range =
