Math 127A (Practice exam II)
October 13, 2010
The practice exam has 4 problems. It is about the same length as the actual exam. It does not represent
every type of problem.
1. For the data given below compute the coefficent of correlation and draw the scatter diagram.
x
y
1
4
2
4
3
2
4
1
5
1
2. The table below gives the values of
x
and 5 possible choices of values for
y
(one choice per column). The
third choice (C) has a correlation coefficient of 0
.
6. Compute the values of the correlation coefficients
for the other choices (A, B, D, E). Explain your reasoning. If you believe that this can not be done in
a simple way, then explain why.
x
choices for
y
A
B
C
D
E
1
1
5
2
3
3
2
2
4
3
3
1
3
3
3
1
3
2
4
4
2
5
3
5
5
5
1
4
3
4
3. Here is some information about the GPAs of business school graduates and their starting salaries.
GPA
Salary
Average
3.0
$85,000
Standard deviation
0.3
$21,000
Correlation coefficient
0.4
You may assume the following: both GPAs and Salaries were normally distributed, the scatter diagram
is footballshaped (Homoscedastic of you prefer), the chance error is normal.
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 Fall '10
 Staff
 Statistics, Correlation, Correlation Coefficient, Normal Distribution, Standard Deviation, Errors and residuals in statistics, regression line

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