Question 3: What assumptions about the data are required for regression analysis and do you think they satisfied here?
We assume that the deviations from the regression line follow a Normal distribution and have uniform variation along the line. The second assumption looks very reasonable from the figure. The spread of the data about the same is very similar all the way along. It is difficult to tell about the Normal distribution. There appears to be some deviation from linearity, as the points tend to be below the line at each end. This may be because the older people will tend to be women, who are smaller than men.
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Last updated: 29 July, 2009.