Suggested answer to exercise: Analyses for qualitative data, 1

Question 1: What is meant by ‘chi-squared = 23.98, P<0.001?’

Suggested answer

This is the result of the chi-squared test which tests the null hypothesis that there is no association between P. alcalifaciens and foreign travel. The value 23.98 is the test statistic which will follow a Chi-squared distribution with 1 degree of freedom if the null hypothesis is true. P<0.001 tells us that the probability of these data or more extreme data occurring if the null hypothesis were true is smaller than 0.001 and so we have good evidence that the null hypothesis is not true and can conclude that an association exists.

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Last updated: 27 July, 2009.

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