The following genuine values are from the 2011 age-structure sheet of the OCR large data set.
| Local Authority | Mean age | Median age |
|---|---|---|
| County Durham | 41.0 | 42 |
| Darlington | 40.2 | 41 |
| Gateshead | 40.5 | 40 |
| Hartlepool | 39.8 | 40 |
Calculate the mean of the four mean ages.
Calculate the median of the four median ages.
Explain why the answer to part (b) is not the median age of all residents in the four Local Authorities combined.
121 exam-style questions on OCR A Level Maths 2.2 Data Presentation and Interpretation, covering 2.2.1 Tables and diagrams for single variable data, 2.2.2 Area in a histogram, 2.2.3 Scatter diagrams and regression lines, 2.2.4 Informal interpretation of correlation, 2.2.5 Correlation and causation, 2.2.6 Measures of average and spread, 2.2.7 Calculations of mean and standard deviation, 2.2.8 Outliers, 2.2.9 Selecting or critiquing data presentation, and 2.2.10 Cleaning data. Each one has a worked solution and a mark scheme showing where the marks go.