ECO 230
Marianna Kudlyak
Economic Statistics
Spring 2007
MIDTERM EXAM I
You have 1 hour and 15 minutes to complete this exam.
Write your answers as clearly and concisely as possible. You may use the calculator the
instructor has provided for you to add and multiply (please return it at the end of the
exam). You may not use your own calculator. You may not use any books or notes. Make
sure to show your reasoning and your work.
There are 6 problems. Total 100 points.
Selected formulas are provided for you on the last page of the exam.
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View Full DocumentProblem 1. [20 points]
State which the following statements are true and which are false? (No explanation
needed; just state “True” or “False”)
1.1.The time it takes you to write a test is an example of categorical variable.
1.2.If two random variables
X
and
Y
are independent, then
P
(
y

x
) =
P
(
x
) and
P
(
x

y
) =
P
(
y
).
1.3.The following data represent a sample of 10 scores on a statistics quiz: 16, 16, 16,
16, 16, 18, 18, 20, 20, and 20. After the range was calculated for the scores, it was
discovered that one of the scores of 20 should have been a 21. The discovery of the
mistake will not change the previously calculated value for range.
1.4.Chebychev’s Theorem states that for any population with mean μ and standard
deviation
σ
, and k>1, the percent of observations that lie within k standard
deviations from the mean is at most 100(1/k
2
)%.
1.5.If event A and event B are mutually exclusive and collectively exhaustive, then the
complement of event A is identical to event B.
1.6.Events A and B are said to be statistically independent if the intersection of event A
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 Spring '08
 Kudlyak
 Probability, Standard Deviation, Probability theory

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