Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2009/iii/paper-102/1/a/solution

The examination used separately emailed files. For this question a public Guerry data archive and its CSV mirror permit a documented reconstruction: retain the 85 records with a recorded region and select the specified columns. All six printed records match exactly, and each of the five regions has 17 departments. The numerical results below refer to that reconstruction; the remaining rows cannot be checked against the unavailable emailed file.
Treat department identifiers as labels and region as a categorical variable. The following summaries show the scale and spread of the quantitative variables:
VariableMeanStandard deviationMedianInterquartile rangeRange
CrimePers19960.947299.241878514790–262215883–37014
CrimeProp7881.343048.6276245990–91901368–20235
Literacy39.1417.433825–5212–74
Donations6723.324863.2449643446–92421246–27830
Wealth rank43.5825.114422–651–86
A larger population-per-crime value means a lower crime rate, and a smaller wealth rank means greater recorded wealth. Donations are markedly right-skewed, as the large gap between mean and median and the upper tail indicate; rank is an ordinal measure rather than a monetary difference. For the ratio analysed next, the median is , the interquartile interval is , and the range is .
Regional median ratios are in C, in E, in N, in S, and in W. The regional box plots and wealth-versus-log-ratio scatter plot in the figure expose this geographical contrast and an inverse association with wealth rank. North has the highest typical property-to-person crime ratio and South the lowest in the reconstructed data. These summaries are descriptive departmental comparisons, not causal or individual-level conclusions.

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