ZIMSEC O Level · Mathematics · Form 2, Form 3, Form 4
Statistics is about collecting, showing and interpreting data.
Averages and spread
- Mean = total of values ÷ number of values.
- Median = middle value when the data is in order.
- Mode = the most common value.
- Range = highest − lowest.
Frequency tables
Mean from a frequency table = Σfx ÷ Σf. For grouped data, use the mid-point of each class as x.
Worked example: Find the mean number of children per household: 0 children (4 homes), 1 (6), 2 (7), 3 (3).
Σfx = 0 + 6 + 14 + 9 = 29; Σf = 20; mean = 29 ÷ 20 = 1.45
Charts and graphs
Bar charts, pie charts (angle = frequency ÷ total × 360°), histograms (frequency density = frequency ÷ class width) and frequency polygons.
Cumulative frequency (Form 4)
Plot cumulative frequency against upper class boundaries. Read the median at ½n, the lower quartile at ¼n and the upper quartile at ¾n. Interquartile range = Q3 − Q1.
Check yourself
- Find the median of 7, 3, 9, 4, 8, 6.
- In a pie chart of 72 learners, 18 walk to school. Find the angle for walkers.
- The mean of five numbers is 12. Four of them are 10, 15, 9 and 14. Find the fifth.
Show answers
- 6.5
- 90°
- 60 − 48 = 12
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