Confidence Intervals

Ok...I can't get this through my thick skull can someone assist please?


A large hospital wholesaler, as part of an assessment of workplace safety, gave a random sample of 40 of its warehouse employees a test (measured on a 0 to 100 point scale) on safety procedures. For that sample of employees, the mean test score was 72 points, with a standard deviation of 6 points. Determine and interpret a 95% confidence interval for the mean test score of all the company’s warehouse employees.

Mean = 72

Standard Deviation of Mean \(\displaystyle = 6 / \sqrt{40}\)

What's next? You tell me.

I know I need to use the upper and lower limits to get the answer but, i am having a hard time with that. Can you assist?

Pretty sure I did. All you are missing is the z-score for 95%.

Ok....so if I have a shaded area of .95 then the area between is 60.2702 and 83.7598...correct?

No. You have answerd a different question. Your answer is for a single random draw.

The question asks for the mean of 40 draws. Look at my first result again.