In a ‘less than’ cumulative frequency distribution of test scores, the data are:
Upper-class limit (marks): 10, 20, 30, 40, 50
Cumulative frequency: 4, 15, 29, 38, 40
In which class interval does the median score lie?
(a) 30–40
(b) 20–30
(c) 10–20
(d) 40–50