Exercises
1. Given a sample of size n = 35 from a N(μ,10) population, the sample mean was found to be 
. Find the following:
. Find the following:
a. A 95% confidence interval for μ
b. A 90% confidence interval for μ
c. A 99% confidence interval for μ
2. Given samples from a normal population with known variance, find the following:
a. The confidence coefficient if n = 16, σ2 = 64, and the total width of the confidence interval for the mean is 3.29 units.
b. The sample size when σ2 = 100 and the 95% confidence interval for the mean is 17.5–22.5.
c. The known variance when n = 100 and the 99% confidence interval for the mean is 23.26 units in width.
3. Assuming random samples from known populations having known standard deviations, find confidence intervals for the population means having the specified degree of confidence:
a. n = 9, 
=20, σ = 3, 1 − α = 0.95
=20, σ = 3, 1 − α = 0.95
b. n = 16, 
=52, σ = 8, 1 − α = 0.99
=52, σ = 8, 1 − α = 0.99
c. n = 25, 
=120, σ = 20, 1 − α = 0.90
=120, σ = 20, 1 − α = 0.90
4. A recent poll asked college juniors how many times they actually sat down and wrote a letter home during the previous academic year. How many students are needed to ...
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