Week7 – Practice Problems’ Solutions
1.
What is the critical value that corresponds to a confidence level of 88%
a.
approximately 1.48
b.
approximately 1.55
CORRECT ANSWER
c.
approximately 1.75
d.
none of these
2.
Compute the margin of error for a 95% confidence interval when sigma is 4 and the sample size
is 36.
3.
A standard IQ test has a mean of 98 and a standard deviation of 16. We want to be 90% certain
that we are within 8 IQ points of the true mean. Determine the sample size.
4.
Interpret a 95% confidence interval of (3.355, 3.445).
a.
There is a 95% probability that the interval (3.355 to 3.445) contains µ, the true
population mean.
5.
The bus driver's union claims that the mean age of bus drivers in Los Angeles is 50.1 years. If a
hypothesis test is performed, how should you interpret a decision that fails to reject the null
hypothesis?
a.
There is not enough evidence to reject the claim by the bus driver's union that the mean
age is 50.1
6.
The bus driver's union claims that the mean age of bus drivers in Chicago is 48.9 years. If a
hypothesis test is performed, how should you interpret a decision that rejects the null hypothesis?
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 Spring '08
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 Statistics, Normal Distribution, Statistical hypothesis testing, mean lifetime

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