# Finding confidence intervals?

#### BrodyF03

##### New member
Past experience indicates that the breaking strength of yarn used in manufacturing drapery material is normallydistributed and that σ = 2 psi. A random sample of 15 specimens is tested and the average breaking strengthis found to be ¯x = 97.5 psi.
(a) Find a 95% confidence interval on the true mean breaking strength.
(b) Find a 99% confidence interval on the true mean breaking strength

#### Ishuda

##### Elite Member
Past experience indicates that the breaking strength of yarn used in manufacturing drapery material is normallydistributed and that σ = 2 psi. A random sample of 15 specimens is tested and the average breaking strengthis found to be ¯x = 97.5 psi.
(a) Find a 95% confidence interval on the true mean breaking strength.
(b) Find a 99% confidence interval on the true mean breaking strength
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