Data Analysis, Statistics, and Probability
Data Analysis, Statistics and Probability tests how you collect, organise, display and interpret data, and how you estimate chance. Expect tables, bar charts, pie charts, averages, range and simple probability from real contexts such as surveys, tests or weather.
Core rules
- Mean = total of values ÷ number of values.
- Median = middle value when data are ordered; for an even number of values, average the two middle values.
- Mode = most frequent value; range = highest − lowest.
- Probability = number of favourable outcomes ÷ total number of equally likely outcomes.
- Probability is between 0 and 1; probabilities of all outcomes add to 1.
- Read chart scales and labels carefully; a graph can mislead if the axis does not start at zero.
Worked example
Five test scores are 12, 15, 15, 18, 20. Mean = (12 + 15 + 15 + 18 + 20) ÷ 5 = 80 ÷ 5 = 16. Ordered data: 12, 15, 15, 18, 20. Median = 15. Mode = 15. Range = 20 − 12 = 8. If one score is picked at random, P(15) = 2/5 = 0.4.
Traps that cost marks
- Forgetting to order data before finding the median.
- Using the mean when an outlier makes the median more representative.
- Writing probability as 2:5 instead of 2/5, or giving a probability above 1.
- Misreading a pie chart sector or a bar chart axis.