A random sample of 85 group leaders, supervisors, and similar personnel revealed that on the average a person spent 6.5 years on the job before being promoted. The standard deviation of the sample was 1.7 years. What is the 95% confidence interval for the true population mean?
A) 6.46 and 6.54
B) 3.17 and 9.83
C) 6.13 and 6.87
D) 6.20 and 6.70
E) 6.32 and 6.88

Question

Quizplus · Accepted Answer

The 95% confidence interval for the mean is calculated using the formula: mean ± (Z * (standard deviation / sqrt(sample size))). For a 95% confidence level, Z is approximately 1.96. Plugging in the numbers: 6.5 ± (1.96 * (1.7 / sqrt(85))) gives an interval of approximately 6.13 to 6.87.

A Random Sample of 85 Group Leaders, Supervisors, and Similar