A student calculates the percentage of employed people travelling by train for four Local Authorities from the OCR large data set.
| Local Authority | Train count | Employed total | Percentage entered |
|---|---|---|---|
| A | 1865 | 227894 | 0.818 |
| B | 828 | 49014 | 1.69 |
| C | missing | 91877 | 0 |
| D | 469 | 37767 | 1.24 |
Explain why the entry for C should be treated as missing rather than zero.
State two checks that should be made before graphing the percentages.
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.