THOSE ARE THE ONLY ANSWERS WE WILL GRADE.
1.
If A and B are disjoint
then P(AB) equals 0.
a.
TRUE
b. FALSE
2.
One can show that P(A)P(BA) = P(B)P(AB).
a.
TRUE
b. FALSE
3.
The branches on a tree diagram contain marginal and conditional probabilities;
they do not contain “and” probabilities.
a.
TRUE
b. FALSE
4.
The cells in a table represent conditional probabilities.
a.
TRUE
b. FALSE
For Questions 57:
Suppose Bob is planning a trip to visit his cousin in Chicago. We want to
compare the length of his trip (short or long) to whether or not he’ll forget to pack something
important.
Short trip
Long trip
Forgot something important
0.20
0.60
0.80
Didn’t forget something important
0.05
0.15
0.20
0.25
0.75
1.00
5.
If you calculated 0.20 / 0.80 = 0.25 this number would represent:
6.
According to the table above, whether or not Bob forgets something important is
independent of the length of his trip.
7.
Bob goes on more long trips than short trips.
a.
TRUE
b. FALSE
8.
If X and Y are independent, the standard deviation of X + Y equals the standard
deviation of X plus the standard deviation of Y.
9.
If X and Y are independent, the variance of X – Y equals the variance of Y – X.
a.
TRUE
b. FALSE
3
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10.
The mean of a random variable can never be negative.
11.
If P(A) = 0.50, P(B) = 0.30, and P(A and B) = 0.15, then A and B are
independent.
12.
Suppose the percentage of Corvette owners who are women is 25% and the
percentage of Corvette owners who are men is 75%. True or False: Corvette
ownership is independent of gender.
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 Winter '12
 Johnson
 Statistics, Standard Deviation, Probability theory

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