SOLUTION: a. A random sample of size 81 is taken from a large population, measuring the time it takes to complete a driver’s license examination. The sample mean was found to be 43 minute

Question 1182052: a. A random sample of size 81 is taken from a large population, measuring the time it takes to complete a driver’s license examination. The sample mean was found to be 43 minutes, and the sample standard deviation 5.71 minutes. Construct a 95% confidence interval around the sample mean. Be sure to show whether you use the t- or z- value, and what value you use. Please use the exact value appropriate for these circumstances (rather than the approximations sometimes referred to as the empirical rule). Interpret the confidence interval in a single sentence. In another sentence, state why you used either the “t” or the “z”.
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
We don't know the sd of the population, only that it is large (and probably normal).
This means we will use a t-test
half-interval for 95%CI is t (0.975,df=80)*s/sqrt(n)
=1.99*5.71/9
=1.26
the interval is (41.74, 44.26) min
We don't know the exact mean of the population, but we are highly (95%) confident it lies in the interval shown.

RELATED QUESTIONS
a random sample of size 36 is taken from a population whith mean of 50 and standard... (answered by tommyt3rd)

Consider a large population with a mean of 100 and a standard deviation of 21. A random... (answered by robertb)

Assume 50 random samples of the same sample size are taken from a population, and a 90%... (answered by keilewis)

It is known that the time it takes to mark assignments are normally distributed with a... (answered by Theo)

samples of size 81 are taken from a population of size 500 with mean 10 and standard... (answered by CPhill)

is known that the time it takes to mark assignments are normally distributed with a... (answered by Boreal)

Determine the mean (μx̅), variance (σ2 x̅), and standard deviation (σx̅). a. (answered by Boreal)

a) If a random sample of size n = 6 is taken from a population, what is required in order (answered by Boreal)

Consider an infinite population with a mean of 160 and a standard deviation of 25. A... (answered by stanbon)