The following genuine counts are from the 2011 age-structure sheet of the OCR large data set.
| Local Authority | All usual residents | Age 65–74 | Age 75–84 | Age 85–89 | Age 90 and over |
|---|---|---|---|---|---|
| County Durham | 513242 | 50883 | 30635 | 7321 | 3506 |
| Darlington | 105564 | 9717 | 6172 | 1740 | 810 |
Calculate the proportion aged 65 or over for each Local Authority.
Calculate the proportion aged 65 or over in the two Local Authorities combined.
Explain why the combined proportion is not the arithmetic mean of the answers to part (a).
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.