Question 6: What would be the advantages and disadvantages compared to a chi-squared test for association in a contingency table?
The test for trend takes into account the ordering of the age groups, which the ordinary contingency table chi-squared does not. Hence the test for trend has much greater power to detect a steady increase (or decrease) in seropositivity with age. However the test has less power to detect non-linear relationships, such as seropositivity being higher among younger men and older men than among those in the middle of the age range. Such a relationship would produce a non-significant trend test.
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