The age distribution of members of a community sports club is given below.
(a) Age (years): Below 20 | 20–40 | 40–60 | 60–80 | 80 and above
Frequency: 6 | 12 | 18 | 9 | 5
(b) (i) Choose suitable class mid-points for the first and the last class and write the complete list of mid-points for all five classes.
(c) (ii) Using the mid-points chosen in part (i), compute the mean age of the members.
(d) (iii) Determine the population standard deviation of the age distribution.
(e) (iv) Briefly comment on how the open-ended classes may affect the accuracy of your result in part (iii).