Given the sample mean, population standard deviation, and confidence level, use the one-mean z-interval procedure to find a confidence interval for the mean of the population.

X‾ =25 , n = 36 , σ = 3 , Confidence level = 95%

Given the sample mean, population standard deviation, and confidence level, use the one-mean z-interval procedure to find a confidence interval for the mean of the population.

X‾ =25 , n = 36 , σ = 3 , Confidence level = 95%

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When you want a 95% confidence interval for µ (population mean) and σ (population standard deviation) is known, we use the formula:

X-bar ± Z_{.975}*σ/√n

X-bar is the sample average

Z_{.975} is the critical value for which if Z~Normal(0,1) then P(Z<Z_{.975}) = .975. This can be looked up on a Normal table. Make sure you are able to use these tables, but Z_{.975 }= 1.96.

σ is the population standard deviation

n is the sample size

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