The table gives brain sizes and IQs for 10 subjects. We want to find the best predicted IQ of someone with a brain size of 1275 cm3.
Brain Size (cm3) |
965 |
1029 |
1030 |
1285 |
1049 |
1077 |
1037 |
1068 |
1176 |
1105 |
IQ |
90 |
85 |
86 |
102 |
103 |
97 |
124 |
125 |
102 |
114 |
Should we use linear regression? We need to examine the data and decide whether regression is appropriate. If it is, we can obtain a prediction from the regression line. If it is not appropriate, we should simply use the mean IQ score as the best predictor.
Source: Elementary Statistics, 11th edition, Mario Triola
Determine the linear regression line for brain size vs. IQ using the data provided. Decide whether linear regression is appropriate. What is the best predictor of IQ in this case: brain size or mean IQ?
Use Excel to create a trendline -
Use Statdisk to do linear regression -
Based on the regression, with a brain size of 1275 cm3 we would predict an IQ of 71.8+0.0286(1275) = 108.
But since a linear relation is not supported, we would instead use the mean IQ score of 100 as the best predictor, independent of brain size.
