Before purchasing videoconferencing$$ equipment, a company tested its current internal computer network. The tests measured how rapidly data moved through its network given the current demand on the network. Eighty files ranging in size from $20$ to $100$ megabytes$($MB$)$ were transmitted over the network at various times of$$ day, and the time to send the files$($in seconds$)$ recorded. In the accompanying$$ data, the time is given as the number of hours past $8$ A$.$M$.$ on the day of the test. Use the transfer time as the$$ response, with the file size and time of day as explanatory variables. Complete parts$($a$)$ through$($f$)$ below.

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Part $1$

$($a$)$ Examine scatterplots of the response versus the two explanatory variables as well as the scatterplot between the explanatory variables. Are there any unusual features in the$$ data? Do the relevant plots appear straight enough for multiple$$ regression?

Construct a scatterplot of Transfer Time on File Size. Choose the correct graph below.

A$.$

$20$

$100$

$0$

$60$

File Size $($MB$)$

Transfer Time $($sec$)$

A set of coordinate axes with a horizontal axis titled "File Size $($MB$)"$ that ranges from $20$ to $100$ in increments of $10$ and a vertical axis titled "Transfer Time $($sec$)"$ that ranges from $0$ to $60$ in increments of $6.$ A series of points are plotted that do not vary much and closely follow an imaginary line that rises from left to right, with some curvature at the ends.

B$.$

$20$

$100$

$0$

$60$

File Size $($MB$)$

Transfer Time $($sec$)$

A set of coordinate axes with a horizontal axis titled "File Size $($MB$)"$ that ranges from $20$ to $100$ in increments of $10$ and a vertical axis titled "Transfer Time $($sec$)"$ that ranges from $0$ to $60$ in increments of $6.$ A series of points are plotted that vary significantly and form a band that rises from left to right.

Your answer is correct.C$.$

$20$

$100$

$0$

$60$

File Size $($MB$)$

Transfer Time $($sec$)$

A set of coordinate axes with a horizontal axis titled "File Size $($MB$)"$ that ranges from $20$ to $100$ in increments of $10$ and a vertical axis titled "Transfer Time $($sec$)"$ that ranges from $0$ to $60$ in increments of $6.$ A series of points are plotted that vary significantly and form a band that falls from left to right.

D$.$

$20$

$100$

$0$

$60$

File Size $($MB$)$

Transfer Time $($sec$)$

A set of coordinate axes with a horizontal axis titled "File Size $($MB$)"$ that ranges from $20$ to $100$ in increments of $10$ and a vertical axis titled "Transfer Time $($sec$)"$ that ranges from $0$ to $60$ in increments of $6.$ A series of points are plotted that do not vary much and closely follow an imaginary line that falls from left to right, with some curvature at the ends.

Part $2$

Construct a scatterplot of Transfer Time on Hours past $8.$ Choose the correct graph below.

A$.$

$0$

$5$

$0$

$60$

Hours past $8$

Transfer Time $($sec$)$

A set of coordinate axes with a horizontal axis titled "Hours past $8"$ that ranges from $0$ to $5$ in increments of $\mathrm{.}5$ and a vertical axis titled "Transfer Time $($sec$)"$ that ranges from $0$ to $60$ in increments of $6.$ A series of points are plotted that vary significantly and form a band that falls from left to right.

B$.$

$0$

$5$

$0$

$60$

Hours past $8$

Transfer Time $($sec$)$

A set of coordinate axes with a horizontal axis titled "Hours past $8"$ that ranges from $0$ to $5$ in increments of $\mathrm{.}5$ and a vertical axis titled "Transfer Time $($sec$)"$ that ranges from $0$ to $60$ in increments of $6.$ A series of points are plotted that do not vary much and closely follow an imaginary line that falls from left to right, with some curvature at the left end.

C$.$

$0$

$5$

$0$

$60$

Hours past $8$

Transfer Time $($sec$)$

A set of coordinate axes with a horizontal axis titled "Hours past $8"$ that ranges from $0$ to $5$ in increments of $\mathrm{.}5$ and a vertical axis titled "Transfer Time $($sec$)"$ that ranges from $0$ to $60$ in increments of $6.$ A series of points are plotted that vary significantly and form a band that rises from left to right.

Your answer is correct.D$.$

$0$

$5$

$0$

$60$

Hours past $8$

Transfer Time $($sec$)$

A set of coordinate axes with a horizontal axis titled "Hours past $8"$ that ranges from $0$ to $5$ in increments of $\mathrm{.}5$ and a vertical axis titled "Transfer Time $($sec$)"$ that ranges from $0$ to $60$ in increments of $6.$ A series of points are plotted that do not vary much and closely follow an imaginary line that rises from left to right, with some curvature at the right end.

Part $3$

Construct a scatterplot of File Size on Hours past $8.$ Choose the correct graph below.

A$.$

$0$

$5$

$20$

$100$

Hours past $8$

File Size $($MB$)$

A set of coordinate axes with a horizontal axis titled "Hours past $8"$ that ranges from $0$ to $5$ in increments of $\mathrm{.}5$ and a vertical axis titled "File Size $($MB$)"$ that ranges from $20$ to $100$ in increments of $10.$ A series of points are plotted that perfectly follow an imaginary line that rises from left to right.

B$.$

$0$

$5$

$20$

$100$

Hours past $8$

File Size $($MB$)$

A set of coordinate axes with a horizontal axis titled