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26. Sisters and brothers (3.1, 3.2) How strongly do physical characteristics of sisters and brothers correlate? Here are data on the heights (in inches)
of 11 adult pairs:

Brother
71
68
66
67
70
71
70
73
72
65
66
Sister
69
64
65
63
65
62
65
64
66
59
62

(a) Construct a scatterplot using brother’s height as the explanatory variable. Describe what you see.
(b) Use your calculator to compute the least-squares regression line for predicting sister’s height from brother’s height. Interpret the slope in context.
(c) Damien is 70 inches tall. Predict the height of his sister Tonya.
(d) Do you expect your prediction in (c) to be very accurate? Give appropriate evidence to support your answer.

Short Answer

Expert verified

(a) A scatterplot using brother’s height as the explanatory variable is weak positive correlation.

(b) The least square regression line equation is y^=27.635+0.527x.

(c) The height of Tonya is 64.525inches.

(d) The coefficient of determination is low. So, the model isn't very accurate.

Step by step solution

01

Part (a) Step 1: Given information

To construct a scatter plot using brother’s height as the explanatory variable with the given data.

Brother
71
68
66
67
70
71
70
73
72
65
66
Sister
69
64
65
63
65
62
65
64
66
59
62
02

Part (a) Step 2: Explanation

The horizontal axis represents the brother, while the vertical axis represents the sister. The scatter plot can be made as follows:

Because the scatterplot slopes upwards, the association is positive. Because the points appear to be far apart, the association is weak. So, there is a weak positive correlation between to variables.

03

Part (b) Step 1: Given information

To use the calculator to compute the least-squares regression line for predicting sister’s height from brother’s height. And interpret the slope in context.

04

Part (b) Step 2: Explanation

The following is the output from a Ti-83 calculator:

As a result, the equation of the regression line is y^=27.635+0.527x.

05

Part (c) Step 1: Given information

To predict the height of his sister Tonya. Since, Damien is 70 inches tall.

06

Part (c) Step 2: Explanation

Tonya's height can be estimated as follows:
y^=27.635+0.527x
=27.635+0.527(70)
=64.525
Asa a result, the height of Tonya's is about 64.525inches.

07

Part (d) Step 1: Given information

To determine the prediction in part (c) to be very accurate or not.

08

Part (d) Step 2: Explanation

Using a Ti-83 calculator, the coefficient of determination can be calculated as follows:

Because the coefficient of determination is low.
As a result, the model isn't very accurate.

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