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Name___________________
STA 6166
Exam #3
Fall 2003
1.
Weights and chest diameter (called heart girth) measurements were made on 539 cattle.
The
objective was to see if weights of these beasts can be estimated based on the chest measurements
(which are easily made with a tape measure) and thereby avoid having to get the animals on a
scale.
Below are summary computations for the data, where
y
=weight in pounds and
x
=heart
girth in inches.
n=539
Σ
x
i
= 82790
Σ
y
i
= 151669 S
xx
= 31093
S
xy
= 130837
S
yy
= 736962
(8) a. Set up computations for the slope and intercept of the equation for the regression line (that
is, show how they are obtained from the summary computations).
Slope:
b
1
=
Intercept:
b
0
=
(8) b. Your equation for the regression line should be
ˆ
365 4.21
yx
=
−+
.
Write interpretations
for the slope and intercept (that is, describe what they mean in terms of weight and hearth girth).
Slope:
Intercept:
(5) c. Sketch a graph of your regression line.
y
= weight
500


400


300


200


100


0 ____________________________________________________
0
50
100
150
200
x
= heart girth
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View Full Document(5) d. The intercept is negative. Does its interpretation have any practical value?
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 Fall '08
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