In: Statistics and Probability
A pediatrician wants to determine the relation that exists between a child's height, x, and head circumference, y. She randomly selects 11 children from her practice, measures their heights and head circumferences, and obtains the accompanying data. Complete parts (a) through (g) below.
Height (inches), x | Head Circumference (inches), y |
28 | 17.7 |
24.25 | 17.3 |
25.5 | 17.2 |
25.75 | 17.7 |
24.5 | 17.0 |
28.25 | 17.8 |
26.75 | 17.5 |
27.25 | 17.5 |
26.75 | 17.5 |
26.75 | 17.7 |
27.5 | 17.7 |
(a) Find the least-squares regression line treating height as the explanatory variable and head circumference as the response variable.
(b) Interpret the slope and y-intercept, if appropriate.
(c) Use the regression equation to predict the head circumference of a child who is
24.5 inches tall.
(d) Compute the residual based on the observed head circumference of the 24 .5 -inch-tall child in the table. Is the head circumference of this child above or below the value predicted by the regression model?
(e) Draw the least-squares regression line on the scatter diagram of the data and label the residual from part (d).
(f) Notice that two children are 26.75 inches tall. One has a head circumference of 17.5 inches; the other has a head circumference of 17.7 inches. How can this be?
(g) Would it be reasonable to use the least-squares regression line to predict the head circumference of a child who was 32 inches tall? Why?