Exercise: Head circumference and height, answer 11

Question 11: What assumptions are required for this test? Do you think they are met here? What further information would you like to assess this?

Suggested answer

We assume that the deviations from the line in the outcome variable, i.e. the differences between the observed head circumferences and those predicted by the regression line, follow a Normal distribution whose variance is uniform, that is, it is unrelated to the magnitude of the predictor variable, height.

We would like a plot of the distribution of the residuals, such as a histogram or Normal plot, and a scatter plot of residuals against height or against the value predicted by the regression:

See detailed description at D. d

See detailed description at D. d

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Last updated: 7 March, 2006.

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