Theory question 108
Statisticsthe marks scored by 35 students in a test are given in the table below:
Marks: 1−5, 6−10, 11−20, 21−30, 31−35, 36−40
No. of students: 2, 7, 12, 8, 5, 1
Draw a histogram for the distribution
Show the model answer
Model answer
Class boundaries 0.5, 5.5, 10.5, 20.5, 30.5, 35.5, 40.5; the class widths are unequal (5, 5, 10, 10, 5, 5)
Bar heights must be frequency densities, e.g. per 5 marks: 2, 7, 6, 4, 5, 1 (or frequency ÷ width: 0.4, 1.4, 1.2, 0.8, 1.0, 0.2)
Draw touching bars over the boundaries with these heights, with a stated scale
Explanation
With unequal class widths the area, not the height, of each bar shows the frequency.