An audit finds that the dollar amounts of invoices have a mean of $1,662 anda standard deviation of $302. What is the probability that for a sample of 50 invoices, the average invoice is less than $1,550?

60% of all the students passed an exam. If a random sample of 10 students is selected, What is the mean and the standard deviation ?

The Greenville Power Authority states that the mean monthly energy bill for their customers is $228 with a standard deviation of $38. They know that energy bills follow a normal distribution. a. Between what two values do we expect 99.7% of energy bill’s to fall? b. What is the probability of a randomly selected energy bill at least $190?

One year, the distribution of salaries for professional sports players had mean $1.6 million and standard deviation $0.81 million. Suppose a sample of 100 major league players was taken. Find the approximate probability that the average salary of the 100 players that year exceeded $1.7 million. Round your answer to nearest ten-thousandth.

Assume the average price for a movie is ​$7.35. Assume the population standard deviation is ​$0.44 and that a sample of 40 theatres was randomly selected. What is the probability that the sample mean will be less than ​$7.31​?

It is known that 41% of the population in the United States have brown eyes. Find the mean and standard deviation for the number of brown eyed people in a random group of 25 people in the United States. I cannot for the life of me figure this problem out.

The NJ Department of Health has reported the average life span of NJ residents is 81 years. If the standard deviation is σ = 4 years, what is the probability of a person living to at least 92 years of age?