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Exercise: BMI and alcohol consumption in the 2005 questionnaire, 4

Question 4: Why would a correlation coefficient be difficult to interpret for this graph?

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Suggested answer

The distribution of alcohol consumption is clearly positively skew and will have a long tail
on the right.

We cannot estimate a confidence interval for *r* unless both variables follow
Normal distributions, so it is difficult to interpret the value of a correlation coefficient.

The test of significance would be OK,
provided BMI followed a distribution which was approximately Normal.

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Last updated: 5 December, 2006.

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