From the OCR 2011 age-structure data, four mean ages are recorded as 41.0,40.2,405,39.8 41.0,40.2,405,39.8\,41.0,40.2,405,39.8 years.
Identify the entry that should be investigated.
Suggest the likely corrected value.
State why the original value should not simply be deleted without checking.
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.