EBook Problems Normal Prob
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Revision as of 06:07, 25 January 2009
EBook Problems Set - Nonstandard Normal Distribution: Finding Probabilities
Problem 1
The Rockwell hardness of certain metal pins is known to have a mean of 50 and a standard deviation of 1.5. If the distribution of all such pin hardness measurements is known to be normal, what is the probability that the average hardness for a random sample of nine pins is at least 50.5?
- Choose one answer.
- (a) Approximately 4
- (b) 0.4
- (c) Approximately 0.1587
- (d) Approximately 0
Problem 2
In an article in the Journal of American Pediatric Health researchers claim that the weights of healthy babies born in the United States form a distribution that is nearly normal with an average weight of 7.25 pounds and standard deviation of 1.75 pounds. The US Department of Health classifies a newborn as "low birth weight" if her/his weight is less than 5.5 pounds. What is the probability that a baby, chosen at random, weighs less than 5.5 pounds?
- Choose one answer.
- (a) About 16%
- (b) About 84%
- (c) About 90%
- (d) the probability cannot be determined
- (e) About 10%
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- SOCR Home page: http://www.socr.ucla.edu
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