Download 1. Use the confidence level and sample data to find a confidence

1. Use the confidence level and sample data to find a confidence interval for estimating the population µ. Round your
answer to the same number of decimal places as the sample mean. Test scores: n = 105; mean x = 70.5; s = 6.8;
99% confidence
Data:
n = 105
x-bar = 70.5
s = 6.8
% = 99
Standard Error, SE = s/√n = 6.8/√105 = 0.6636
Degrees of freedom = 104
t- score = 2.6239
Width of the confidence interval = t * SE = 2.6239 * 0.6636 = 1.7413
Lower Limit of the confidence interval = x-bar - width = 70.5 - 1.7413 = 68.7587
Upper Limit of the confidence interval = x-bar + width = 70.5 + 1.7413 = 72.2413
The 99% confidence interval is [68.8 72.2]
2. Use the given information to find the minimum sample size required to estimate an unknown population mean µ.
How many business students must be randomly selected to estimate the mean monthly earnings of business students
at one college? We want 95% confidence that the sample mean is within $129 of the population mean, and the
population standard deviation is known to be $595.
Confidence Level % = 95
z- score = 1.9600
Population SD, σ = 595
Error, E = 129
Sample Size, N = (z * σ / E)^2 = (1.96 * 595/129)^2 = 82
At least 82 students must be sampled.