MATLAB: An Introduction with Applications
MATLAB: An Introduction with Applications
6th Edition
ISBN: 9781119256830
Author: Amos Gilat
Publisher: John Wiley & Sons Inc
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No-fines concrete, made from a uniformly graded coarse aggregate and a cement-water paste, is beneficial in areas prone to excessive rainfall because of its excellent drainage properties. The article "Pavement Thickness Design for No-Fines Concrete Parking Lots,"+ employed a least
squares analysis in studying how y = porosity (%) is related to x = unit weight (pcf) in concrete specimens. Consider the following representative data.
Relevant summary quantities are Σxi = 1640.2 ΣΥ; = 299,3, Σx? = 179,865,54, Σ×y; = 32,259,22, Σy = 6409.33.
(a) Obtain the equation of the estimated regression line. (Round all numerical values to four decimal places.)
119.3385 -0.9089x
125
Create a scatterplot of the data and graph the estimated line.
120
y
115
110
x 99.2 101.2 102.6
103.1 105.3 107.2 108.5 110.7
y 28.9 27.8 26.9 25.1 22.9 21.4 20.8 19.7
105
x 112.0 112.2 113.8 114.0 115.2 115.3
119.9
y 16.9 18.8 15.9 16.9 12.8 13.5 11.0
100
O
USE SALT
10
15
20
25
30
y
125
120
115
110
105
100
O
10
15
20
(c) Predict porosity when unit weight is 134? (Round your answer to two decimal places.)
ŷ = -2.45
25
(b) Interpret the slope of the least squares line. (Round your answer to four decimal places.)
The slope tells us that a one-pcf increase in the unit weight of a concrete specimen is associated with a -0.696
(e) Calculate a point estimate of a. (Round your answer to two decimal places.)
3.87
X
30
(d) Calculate the residual corresponding to the first observation. (Round your answer to two decimal places.)
-0.28
Calculate the residual corresponding to the second observation. (Round your answer to two decimal places.)
3.01
x
y
30
Does it appear that the model relationship will explain
great deal of the observed variation in y?
Yes
✓✓ the linear model explains a great deal of the variation in y since the accompanying fitted line plot does
25
20
15
10
Why is it not a good idea to predict porosity when unit weight is 134?
When we predict porosity for a unit weight of 134 (which is outside the scope of the data) the result is negative ✓ ✓
100 105 110
which cannot
y
30
25
✔✔✔happen in reality.
20
15
XO
125
120
10
Xpercentage point decrease in the specimen's predicted porosity.
100 105 110
show a very strong, linear association between unit weight and porosity.
115
120
125
expand button
Transcribed Image Text:No-fines concrete, made from a uniformly graded coarse aggregate and a cement-water paste, is beneficial in areas prone to excessive rainfall because of its excellent drainage properties. The article "Pavement Thickness Design for No-Fines Concrete Parking Lots,"+ employed a least squares analysis in studying how y = porosity (%) is related to x = unit weight (pcf) in concrete specimens. Consider the following representative data. Relevant summary quantities are Σxi = 1640.2 ΣΥ; = 299,3, Σx? = 179,865,54, Σ×y; = 32,259,22, Σy = 6409.33. (a) Obtain the equation of the estimated regression line. (Round all numerical values to four decimal places.) 119.3385 -0.9089x 125 Create a scatterplot of the data and graph the estimated line. 120 y 115 110 x 99.2 101.2 102.6 103.1 105.3 107.2 108.5 110.7 y 28.9 27.8 26.9 25.1 22.9 21.4 20.8 19.7 105 x 112.0 112.2 113.8 114.0 115.2 115.3 119.9 y 16.9 18.8 15.9 16.9 12.8 13.5 11.0 100 O USE SALT 10 15 20 25 30 y 125 120 115 110 105 100 O 10 15 20 (c) Predict porosity when unit weight is 134? (Round your answer to two decimal places.) ŷ = -2.45 25 (b) Interpret the slope of the least squares line. (Round your answer to four decimal places.) The slope tells us that a one-pcf increase in the unit weight of a concrete specimen is associated with a -0.696 (e) Calculate a point estimate of a. (Round your answer to two decimal places.) 3.87 X 30 (d) Calculate the residual corresponding to the first observation. (Round your answer to two decimal places.) -0.28 Calculate the residual corresponding to the second observation. (Round your answer to two decimal places.) 3.01 x y 30 Does it appear that the model relationship will explain great deal of the observed variation in y? Yes ✓✓ the linear model explains a great deal of the variation in y since the accompanying fitted line plot does 25 20 15 10 Why is it not a good idea to predict porosity when unit weight is 134? When we predict porosity for a unit weight of 134 (which is outside the scope of the data) the result is negative ✓ ✓ 100 105 110 which cannot y 30 25 ✔✔✔happen in reality. 20 15 XO 125 120 10 Xpercentage point decrease in the specimen's predicted porosity. 100 105 110 show a very strong, linear association between unit weight and porosity. 115 120 125
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