Suppose that,on average,electricians earn approximately µ = $54,000 per year in the United States.Assume that the distribution for electricians' yearly earnings is normally distributed and that the standard deviation is σ = $12,000.What is the probability that the average salary of four randomly selected electricians is less than $50,000?
A) 0.2514
B) 0.3707
C) 0.6293
D) 0.7486

Question

Quizplus · Accepted Answer

The standard error for the sample mean is σ/√n = $12,000/√4 = $6,000. The z-score for $50,000 is (50,000 - 54,000) / 6,000 = -0.67. Using the standard normal distribution table, the probability of a z-score less than -0.67 is approximately 0.2514.

Suppose That,on Average,electricians Earn Approximately µ = $54,000 Per Year