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George Mason University
School of Management
OM 210:
STATISTICAL ANALYSIS FOR MANAGEMENT
Prof. Harvey Singer
TEST #3:
Inference and Regression (SAMPLE)
Confidence Interval Example Problems
1. A process packages refined sugar into small 20ounce bags.
The weights of the
contents of these bags (net weight) have a standard deviation of 1.2 ounces.
A
random sample of 36 bags had mean net weight 19.8 ounces.
a. What is the point estimate for the mean bag weight?
b.
On the basis of this point estimate, what do you suspect?
c. Calculate the margin of error at 95% confidence.
d. Calculate and interpret the 95% confidence interval based on the sample
findings for the true mean weight for all bags of sugar produced by this
process.
e. At 95% confidence, what is the chance that the true mean is actually larger
than the upper bound of the 95% confidence interval found in d?
f. What is the chance that, on average, a bag is actually filled with 20 ounces of
sugar?
g. Based on your results so far, is there a statistical basis for suspecting that the
bags being underfilled, on average?
h. Find the margin of error between the true and sampled mean net weights at
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This note was uploaded on 02/19/2011 for the course OM 210 taught by Professor Singer during the Spring '08 term at George Mason.
 Spring '08
 SINGER

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