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Question 3-10 marks A random sample of 90 observations produced a mean

`\bar{x} =25.9`

and a standard deviation

`s=2.7`

. a. Find a

`95%`

confidence interval for the population mean

`\mu `

. b. Find a

`90%`

confidence interval for

`\mu `

. c. Find a

`99%`

confidence interval for

`\mu `

. \table[[Table 7.2 Commonly Used Values of

`z_((\alpha )/(2))`

,,,],[Confidence Level,,,],[

`100(1-\alpha )%`

,

`\alpha `

,

`(\alpha )/(2)`

,

`z_((\alpha )/(2))`