The Quantitative Environmental Learning Project presented data on height and circumference of a sample of Douglas fir trees.2 Notice that heights level off after circumferences exceed about 4 meters.
Which one of the following conditions for a regression model is not met:
a. Scatterplot should appear linear.
b. Sample size should be large enough to offset non-normality in responses.
c. Spread of responses should appear fairly constant over the range of explanatory values.
d. Explanatory/response values should constitute a random sample of independent pairs.