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Braking distance, again How is the braking distance for a car related to the amount of tread left on the tires? Here are the braking distances (measured in car lengths) for a car making a panic stop in standing water, along with the tread depth of the tires (in 1/32inch):

Tread depth (1/32 inch)Breaking distance (car lengths)119.7109.8910.1810.4710.8611.2511.8412.4313.6115.2

a. Transform both variables using logarithms. Then calculate and state the least-squares regression line using the transformed variables.

b. Use the model from part (a) to calculate and interpret the residual for the trial when the tread depth was 3/32 inch.

Short Answer

Expert verified

a). The least-squares regression line using the transformed variables is logy=-0.2690+1.2609logx.

b). The expected breaking distance is 2.1508 car length.

Step by step solution

01

Part (a) Step 1: Given Information

Given data:

Tread depth (1/32 inch)Breaking distance (car lengths)119.7109.8910.1810.4710.8611.2511.8412.4313.6115.2

02

Part (a) Step 2: Explanation

Log of given data:

Tread depth (1/32 inch)Breaking distance (car lengths)log(Tread depth)log(length)119.71.0413926850.98677173109.810.99122608910.10.9542425091.00432137810.40.9030899871.01703334610.80.845098041.03342376611.20.778151251.04921802411.80.6989700041.07188201312.40.6020599911.09342169113.60.4771212551.1335389115.20.3010299961.18184359118.301.26245109

Using the calculator Ti83/84

Step 1: Select STAT;

Step 2: Select 1: EDIT

Step 3: in list L1, type the data for logarithmic Tread depth, and in list L2, type the data for logarithmic Braking Distance.

Step 4: hit STAT once more, select CALC, and then LinReg(a+bx).

03

Part (a) Step 3: Explanation

The final result

y=a+bx

a=-0.2690

b=1.2609

Substituting the value in aandb:

y=-0.2690+1.2609x

The logarithm of tread depth is x, whereas the logarithm of braking distance is y.
role="math" localid="1654266116493" logy=-0.2690+1.2609logx

04

Part (b) Step 1: Given Information

Given data:

Tread depth (1/32 inch)Breaking distance (car lengths)119.7109.8910.1810.4710.8611.2511.8412.4313.6115.2

05

Part (b) Step 2: Explanation

Substituting the value xby 3:

logy=-0.2690+1.2609logx

logy=-0.2690+1.2609log3

logy=0.3326

Using the exponential function with a base of ten:

y=10logy

=100.33263

=2.1508

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