Answer:
Step-by-step explanation:
We want to determine a 90% confidence interval for the mean salaries of college graduates
Number of sample, n = 40
Mean, u = $62, 200
Standard deviation, s = $11,766
For a confidence level of 90%, the corresponding z value is 1.645. This is determined from the normal distribution table.
We will apply the formula
Confidence interval
= mean +/- z ×standard deviation/√n
It becomes
62200 +/- 1.645 × 11766/√40
= 62200 +/- 1.645 × 1860.4
= 62200 +/- 3060.358
The lower end of the confidence interval is 62200 - 3060.358 =59139.642
The upper end of the confidence interval is 62200 + 3060.358 =65260.358
Therefore, with 90% confidence interval, the mean mean salaries of college graduates is between $59139.642 and $65260.358
