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joemama69
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Homework Statement
Measure of Contaminatino has a normal distribution w/ unknown mean and unknown variance. Random sample of n=40 provides sample mean = 28.30 and sample variance = 17.38
1)Find Upper 95% Confidence Interval
2)Test Null Hyp = 25.5 vs Alt Hyp = 28.30... Upper Tailed
Homework Equations
The Attempt at a Solution
1)...95% CI... therefore z(1.645) = 95%
(xbar)+z sqrt(sigma^2 / n) = 28.30 + 1.645 sqrt(17.38 / 40) = 28.30 + 1.0843=29.38
(0 < u < 29.38)
2) Test Null Hyp = 25.5 vs Alt Hyp = 28.30... Upper Tailed
Since n = 40 we do not to use T-Tables and can just compute the P-Value from Z-Table.
Z=(x-u)/sqrt(sigma^2/n) = (28.30 - 25.50)/sqrt(17.38 / 40) = z(4.25) = 1.00 ?
Since it us upper tailed P-Value = 1-z(4.25) = 1-1 = 0 ?
Where did I go wrong... Based on my 95% CI, Shouldnt I get a little less than 95% for a value lessthan 29.38?