Stage 9 - Q5 - 4 marks
20231
A pupil averages the five class midpoints and reports \(40\) minutes. Explain the flaw and calculate the correct estimated mean.
Time (min)
Frequency
\(15\le t<25\)
5
\(25\le t<35\)
8
\(35\le t<45\)
16
\(45\le t<55\)
10
\(55\le t<65\)
6
Hint
A class with twenty observations must count more than a class with two.