1. (3 points) Write the four slopes of the four regression lines from the four s
ID: 3364513 • Letter: 1
Question
1. (3 points) Write the four slopes of the four regression lines from the four samples on the "Samples" sheet.
Slope 1 = _________ Slope 2 = __________Slope 3 = __________Slope 4= __________
Compute the standard deviation of the four slopes. s.d. of the slopes = _____________
2. (2 points) Use the sample on top of "Samples "sheet and its scatterplot. (Sample 1)
a. According to the model, how much will a car depreciate per 1,000 miles increase in mileage. (1 point)
b. Based on the above sample predict price for a car with 65,000 miles. (1 point)
3. (2 points)
On "PopulationOrdered" sheet the same data are ordered by mileage.
Copy /paste prices of cars that have mileage of 65,001 to 65,999 miles to the highlighted column starting with cell "D2".
Check the average in cell "G1", this is population mean for 65K cars.
In 2(b) above, you used the regression model to predict the price for a 65K. What is the difference beteween this prediction and the population mean? Why the prediction is off?
Answer:
4. (2 points) Don't use any chapter 10 material to answer this question.
Use the standard deviation of the four slopes in (1). Note that this standard deviation represents approximate value of the standard error of the slope, sample to sample variability of the slope.
a) compute the average slope of the four samples Answer:___________________
b) how many standard errors is -0.2 away from the value in(a) Answer:_________________
Would that be unusual to obtain a sample that results in a slope of - 0.2? Answer:__________________
(Unusual is defined as two standard deviations away)
5. (3 points) Use each of your samples from "Samples" sheet to calculate predicted price for a car with 65,000 miles.
Based on the above four predictions suggest a reasonable interval estimate for the price of 65,000 miles car.
Explain why you suggest this interval.
y-0.0675x +10.421 R: = 0.2952 Sample 1 70.7 80.49 66.16 68.7 57.09 47.1 70.17 79 48.26 61.23 3.65 6.14 6.74 6.86 4.97 8.53 6.37 4.16 6.64 6.35 10 60 100 120 Mileage (1000 miles) y -0.0655x + 10.439 Rz = 0.5 278 46.05 68.5 98.19 62.21 82.52 64.85 74.46 44.57 44.74 63.47 7.34 5.85 5.36 5.59 3.15 6.75 6.49 8.78 7.52 10 8 2 40 60 80 100 120 Mileage (1000 miles)Explanation / Answer
-0.0675, -0.0655,
sd of the slopes = 11.487, 17.34
a) car will depreciate by the slope times for every 1000 miles increase in mileage
$6033.5 for 65000 miles
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