Question 185365
A random sample of 10 miniature Tootsie Rolls was taken from a bag. Each piece was weighed on a very accurate scale. The results in grams were
3.087 3.131 3.241 3.241 3.270 3.353 3.400 3.411 3.437 3.477
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Find the sample mean: I'll call it "m"=3.30480 
Find the standard deviation of the sample: I'll call it "s" = 0.13199.
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(a) Construct a 90 percent confidence interval for the true mean weight.
Find the "standard error" which is designated "E".
E = t*(s/sqrt(n)) = 1.833(0.13199/sqrt(10)) = 0.0765
Then 90% CI is : m-E < u < m+E
3.2283 < u < 3.3813
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(b) What sample size would be necessary to estimate the true weight with an error of �} 0.03 grams with 90 percent confidence?
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Use the "E" formula; but solve it for "n"
n= (s/E)^2
n = {0.13199/0.03)^2 = 19.35
Rounding up you get n = 20
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(c) Discuss the factors which might cause variation in the weight of Tootsie Rolls during manufacture.
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I'll leave that to you.
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Question: I amswered this question several weeks ago, so I went
to the file of "answered Probability and Statistics problems"
and copied my old answer.  Can you enlighten me as to why you
did not find the answer to your question there?  The vast 
majority of word problems from the Doane and Seward Stat book
can be found in that file.
Just wondered.
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Cheers,
Stan H.