Questions about Confidence Interval

May 2010
3
0
Hi,
I could not find the answer of these two questions, can anyone help me ?
thanks in advance.

[FONT=&quot]1- [/FONT][FONT=&quot]A tool manufacturer’s choose randomly 10 pieces from a batch. The measured weights are listed below. Supposing the distribution as normal, please calculate 99% CI of the population variance. [/FONT]
[FONT=&quot](51, 50, 60, 53, 59, 54, 56, 51, 59, 58)[/FONT]


[FONT=&quot]2- [/FONT][FONT=&quot]450 pieces of a machine tool have been produced with a variance of 300 grams2 . Please find for variance the CI of 95%. (solve the problem as a large sample)[/FONT]
 
Apr 2010
14
0
hello
for 1:
first find the variance and the average of the numbers,name them s,u then use this equation?:

T=(Xn-u)/(s/sqrt(n)) ~ t(n-1)
a=.99 -> 1-a=.01
p(-Ta/2<T<Ta/2) =p(-T.05<T<T.05) find this from the table of the t distribution.
for 2 is also as above
 

mr fantastic

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Zeitgeist
Hi,
I could not find the answer of these two questions, can anyone help me ?
thanks in advance.

[FONT=&quot]1- [/FONT][FONT=&quot]A tool manufacturer’s choose randomly 10 pieces from a batch. The measured weights are listed below. Supposing the distribution as normal, please calculate 99% CI of the population variance. [/FONT]
[FONT=&quot](51, 50, 60, 53, 59, 54, 56, 51, 59, 58)[/FONT]


[FONT=&quot]2- [/FONT][FONT=&quot]450 pieces of a machine tool have been produced with a variance of 300 grams2 . Please find for variance the CI of 95%. (solve the problem as a large sample)[/FONT]
Read this: Estimating the Variance

hello
for 1:
first find the variance and the average of the numbers,name them s,u then use this equation?:

T=(Xn-u)/(s/sqrt(n)) ~ t(n-1)
a=.99 -> 1-a=.01
p(-Ta/2<T<Ta/2) =p(-T.05<T<T.05) find this from the table of the t distribution.
for 2 is also as above
You have misread the question. Confidence interval for the variance (NOT the mean) is required.