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1
Economic Statistics
Econ 321
Homework 3:
due Tuesday June 15
Solve the following problems. Explain your logic and show your steps.
1.
Two dice are thrown and their sum is recorded.
a.
Draw (by hand) a graph of the distribution of the sum.
b.
What is the mean and variance of this distribution?
c.
What is the probability that the sum is 9 or greater?
2.
The probability of passing an exam in the statistics class is 30%. A sample of four students is randomly selected.
a.
What is the probability that zero of the students in the sample failed the midterm?
b.
What is the probability that zero of the students in the sample passed the midterm?
c.
What is the mean and standard deviation of the distribution of the number of students who passed the
midterm in the sample?
d.
Draw (by hand) a graph of this distribution. Is it positively or negatively skewed? How would the
skewness change if the probability of passing the exam increased?
3.
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 Spring '11
 chugh

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