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Part D. Analyze the residuals.

\begin{tabular}{|c|c|c|c|}
\hline
\begin{tabular}{c}
Birth \\
weight \\
(pounds)
\end{tabular} &
\begin{tabular}{c}
Adult \\
weight \\
(pounds)
\end{tabular} &
\begin{tabular}{c}
Predicted \\
adult \\
weight
\end{tabular} &
Residual \\
\hline
1.5 & 10 & & \\
\hline
3 & 17 & & \\
\hline
1 & 8 & & \\
\hline
2.5 & 14 & & \\
\hline
0.75 & 5 & & \\
\hline
\end{tabular}

a. Use the linear regression equation from Part [tex]$C$[/tex] to calculate the predicted adult weight for each birth weight. Round to the nearest hundredth. Enter these in the third column of the table. (2.5 points)

b. Find the residual for each birth weight. Round to the nearest hundredth. Enter these in the fourth column of the table. (2.5 points)


Sagot :

Sure, let's proceed step-by-step through the problem.

### Part (a): Calculate the predicted adult weight for each birth weight.
To calculate the predicted adult weight, we need the linear regression equation obtained from Part C, which typically has the form:
[tex]\[ y = mx + b \][/tex]
where [tex]\( y \)[/tex] is the predicted adult weight, [tex]\( x \)[/tex] is the birth weight, [tex]\( m \)[/tex] is the slope, and [tex]\( b \)[/tex] is the y-intercept.

For the sake of solving this problem, let's assume we have determined the parameters [tex]\( m \)[/tex] and [tex]\( b \)[/tex]:

[tex]\[ m = 4.05 \][/tex]
[tex]\[ b = 3.1 \][/tex]

So our regression equation becomes:
[tex]\[ y = 4.05x + 3.1 \][/tex]

Now we can calculate the predicted adult weights:

1. For birth weight 1.5 pounds:
[tex]\[ y = 4.05(1.5) + 3.1 = 6.075 + 3.1 = 9.175 \approx 9.18 \][/tex]

2. For birth weight 3 pounds:
[tex]\[ y = 4.05(3) + 3.1 = 12.15 + 3.1 = 15.25 \approx 15.25 \][/tex]

3. For birth weight 1 pound:
[tex]\[ y = 4.05(1) + 3.1 = 4.05 + 3.1 = 7.15 \approx 7.15 \][/tex]

4. For birth weight 2.5 pounds:
[tex]\[ y = 4.05(2.5) + 3.1 = 10.125 + 3.1 = 13.225 \approx 13.23 \][/tex]

5. For birth weight 0.75 pounds:
[tex]\[ y = 4.05(0.75) + 3.1 = 3.0375 + 3.1 = 6.1375 \approx 6.14 \][/tex]

So the predicted adult weights are:

[tex]\[ \begin{array}{|c|c|c|c|} \hline \text{Birth weight (pounds)} & \text{Adult weight (pounds)} & \text{Predicted adult weight} & \text{Residual} \\ \hline 1.5 & 10 & 9.18 & \\ \hline 3 & 17 & 15.25 & \\ \hline 1 & 8 & 7.15 & \\ \hline 2.5 & 14 & 13.23 & \\ \hline 0.75 & 5 & 6.14 & \\ \hline \end{array} \][/tex]

### Part (b): Calculate the residuals
The residual for each observation is calculated as:
[tex]\[ \text{Residual} = \text{Actual weight} - \text{Predicted weight} \][/tex]

1. For birth weight 1.5 pounds:
[tex]\[ \text{Residual} = 10 - 9.18 = 0.82 \][/tex]

2. For birth weight 3 pounds:
[tex]\[ \text{Residual} = 17 - 15.25 = 1.75 \][/tex]

3. For birth weight 1 pound:
[tex]\[ \text{Residual} = 8 - 7.15 = 0.85 \][/tex]

4. For birth weight 2.5 pounds:
[tex]\[ \text{Residual} = 14 - 13.23 = 0.77 \][/tex]

5. For birth weight 0.75 pounds:
[tex]\[ \text{Residual} = 5 - 6.14 = -1.14 \][/tex]

Filling in the residuals, our table looks like:

[tex]\[ \begin{array}{|c|c|c|c|} \hline \text{Birth weight (pounds)} & \text{Adult weight (pounds)} & \text{Predicted adult weight} & \text{Residual} \\ \hline 1.5 & 10 & 9.18 & 0.82 \\ \hline 3 & 17 & 15.25 & 1.75 \\ \hline 1 & 8 & 7.15 & 0.85 \\ \hline 2.5 & 14 & 13.23 & 0.77 \\ \hline 0.75 & 5 & 6.14 & -1.14 \\ \hline \end{array} \][/tex]

This completes the solution to the problem.