Worked example The data shows the mass (in kg) of the school bags of a group of students: 5 ⋅ 5 7 ⋅ 0 5 ⋅ 7 7 ⋅ 3 5 ⋅ 5 5 ⋅ 9 6 ⋅ 4 7 ⋅ 2 6 ⋅ 0 4 ⋅ 8 5 ⋅ 8 5 ⋅ 4 6 ⋅ 9 5 ⋅ 1 6 ⋅ 3 7 ⋅ 8 7 ⋅ 5 6 ⋅ 4 6 ⋅ 5 5 ⋅ 7 (i) Complete the grouped frequency table:
Mass (kg) 4–5 5–6 6–7 7–8
No. of bags Note: 4–5 means 4 or more, but less than 5
(ii) Find the modal group for this data. (iii) Find the median group. (iv) Estimate the mean, correct to one decimal place, for the grouped frequency table. (v) Calculate the mean from the raw data and comment on which is the more accurate value.
Solution (i)
(ii) (iii)
(iv)
(v)
The responses gathered are known as the ‘raw data’.