Theory question 107
StatisticsThe table shows the age distribution in years of a group of people.
Age (in years): 1 − 5, 6 − 10, 11 − 15, 16 − 20, 21 − 25, 26 − 30
Number of People: 18, 12, 25, 15, 20, 10
Using an assumed mean of 13 years, find the mean age of the people.
Show the model answer
Model answer
Class marks 3, 8, 13, 18, 23, 28; d = x − 13 = −10, −5, 0, 5, 10, 15.
Σf = 100; Σfd = −180 − 60 + 0 + 75 + 200 + 150 = 185.
Mean = 13 + 185/100 = 14.85 years.
Explanation
Mean = A + Σfd/Σf.