Paper 3 · June 2023 · Statistics: measurement scales, Poisson, chi-square, spatial autocorrelation
A chi-square test on cholera cases by age and sex at Musiso Mission hospital gives a test statistic of about 0.08 with 2 degrees of freedom, against a 5 per cent critical value of 5.991. What is the correct conclusion?
AReject the null hypothesis: there is a significant association, so age and sex are dependent factors in these cases.
BThe test is invalid because a chi-square statistic that small indicates the expected frequencies were calculated wrongly.
CNo conclusion is possible without also calculating the correlation coefficient between the age and sex columns.
DDo not reject the null hypothesis: there is no significant association, so age and sex are independent factors in these cases.
Explanation
The calculated statistic, 0.08, is far below the critical value of 5.991, so the null hypothesis of independence stands. The observed counts sit almost exactly on the expected counts, which is precisely why the statistic is so small.
Derived from ZIMSEC Advanced Level Geography 6037/3 Paper 3 Practical Test, June 2023 session, Q1