A grouped frequency distribution has the following information:
• Total observations N=90
• Lower limit of the median class l=30
• Class width h=10
• Cumulative frequency of the class preceding the median class c=40
• Frequency of the median class f=20
Calculate the median of the distribution.
(a) 35.0
(b) 32.5
(c) 37.5
(d) 30.25