Question 6.89

54. A study of reading ability in schoolchildren chose 60 fifth-grade children at random from a school. The researchers obtained the children’s scores on an IQ test and on a test of reading ability. Figure 6.24 plots reading test score (response variable) against IQ score (explanatory variable).

  1. Explain why we should expect a positive association between IQ score and reading score for children in the same grade.
  2. Does the scatterplot show a positive association?
  3. Four points in a group appear to be outliers. In what way do these children’s IQ and reading scores deviate from the overall pattern?
  4. Ignoring the outliers, is the form of the association between IQ score and reading score roughly a straight line? Is it very strong? Explain your answers.