
Concept explainers
(a)
To find the equation of the line of the best fit for the dataand plot the data-
(a)

Answer to Problem 20E
The equation of the best fit of the line is y=7x−95 .
Explanation of Solution
Given:
Formula Used:
The line of fit is the line that most closely goes through the points of data.
The equation of a line is written as y=mx+b where m is the slope and b is the y -intercept.
m=y2−y1x2−x1
Calculation:
Given is −
Plotting the above points on the graph, we have:
Considering the below two points as they fall on the same straight line, we have:
(26,87) and (27,94)
Thus, we have:
Slope =m=y2−y1x2−x1
m=94−8727−26m=7
Thus, the equation of the line is
y−y1=m(x−x1)
y−87=7(x−26)y−87=7x−182y=7x−95
Thus, the equation of the best fit of the line is y=7x−95 .
Conclusion:
The equation of the best fit of the line is y=7x−95 .
(b)
To identify and interpret the
(b)

Answer to Problem 20E
The correlation co-efficient is 0.9357 .
Explanation of Solution
Given:
Formula Used:
The formula to calculate correlation co-efficient is -
r=n(∑xy)−(∑x)(y)√[n∑x2−(∑x)2][n∑y2−(y)2]
Calculation:
Given is −
Using the above formula to calculate correlation co-efficient, we have -
r=n(∑xy)−(∑x)(y)√[n∑x2−(∑x)2][n∑y2−(y)2]
x | y | xy | x2 | y2 |
27 | 94 | 2538 | 729 | 8836 |
18 | 56 | 1008 | 324 | 3136 |
25 | 58 | 1450 | 625 | 3364 |
32 | 123 | 3936 | 1024 | 15129 |
18 | 60 | 1080 | 324 | 3600 |
26 | 87 | 2262 | 676 | 7569 |
36 | 145 | 5220 | 1296 | 21025 |
Thus, we have:
r=n(∑xy)−(∑x)(y)√[n∑x2−(∑x)2][n∑y2−(y)2]
r=0.9357
Conclusion:
The correlation co-efficient is 0.9357 .
(c)
To interpret the slope and y-intercept of the line of the best fit-
(c)

Answer to Problem 20E
The slope is 7 and y -intercept is −95 .
Explanation of Solution
Given:
Formula Used:
The line of fit is the line that most closely goes through the points of data.
The equation of a line is written as y=mx+b where m is the slope and b is the y -intercept.
m=y2−y1x2−x1
Calculation:
Given is −
Equation of the best fit of the line is y=7x−95 .
m=7
y -intercept =−95
Thus, Slope is 7 and y -intercept is −95 .
Conclusion:
The slope is 7 and y -intercept is −95 .
(d)
To find the cost of sailboat that is 20 feet long.
(d)

Answer to Problem 20E
The cost of sailboat that is 20 feet long is 45 (thousands of dollars).
Explanation of Solution
Given:
Formula Used:
The line of fit is the line that most closely goes through the points of data.
The equation of a line is written as y=mx+b where m is the slope and b is the y -intercept.
m=y2−y1x2−x1
Calculation:
Given is −
Equation of the best fit of the line is y=7x−95 .
Since, x=20
y=45
Conclusion:
The cost of sailboat that is 20 feet long is 45 (thousands of dollars).
(e)
To find the length of sailboat that costs $147000 .
(e)

Answer to Problem 20E
The length of sailboat that costs $147000 is 34.57 feet.
Explanation of Solution
Given:
Formula Used:
The line of fit is the line that most closely goes through the points of data.
The equation of a line is written as y=mx+b where m is the slope and b is the y -intercept.
m=y2−y1x2−x1
Calculation:
Given is −
Equation of the best fit of the line is y=7x−95 .
Since, y=147
x=34.57
Thus, the length of sailboat that costs $147000 is 34.57 feet.
Conclusion:
The length of sailboat that costs $147000 is 34.57 feet.
Chapter 4 Solutions
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