Data Handling and Statistics
What you must understand
Candidates must read and interpret tables, pictograms, bar charts, line graphs and simple pie charts. You need to find the mean (total ÷ number of values), the mode (most frequent), the median (middle value when ordered) and the range (largest minus smallest). You should be able to complete a frequency table and decide which average best describes a set of data. Understanding scale is essential: one symbol or one grid square may stand for 2, 5 or 10 items.
Traps to watch
- Pictogram keys: if one symbol means 5 people, half a symbol means 2.5, so read the key before counting.
- Bar chart scales: check whether each square is 1, 2, 5 or 10 units.
- Mean versus total: the mean is not the total. To find a missing value, use total = mean × number of values.
- Median: always arrange the values in order first, and for an even count take the mean of the two middle values.
- Mode: there may be more than one mode, or none at all.
Worked example
Five learners scored 6, 9, 4, 9 and 7 in a test. Find the mean, mode, median and range.
Total = 6 + 9 + 4 + 9 + 7 = 35. Mean = 35 ÷ 5 = 7. Mode = 9 (it appears twice). Ordered: 4, 6, 7, 9, 9, so median = 7. Range = 9 − 4 = 5.
Rule of thumb: for any data question, first write down the total and the count - most statistics follow from those two numbers.