The electric bills for all households in a large city have the normal distribution with a mean of $68 per month and a standard deviation of $10. Find the probability that an electric bill is greater than $70.

The owner of a computer repair shop has determined that their daily revenue has mean $7200 and standard deviation $1200. The daily revenue totals for the next 30 days wil be monitored. What is the probability that the mean daily revenue for the next 30 days will be between $7000 and $7500?

Proctor & Gamble reported that an American family of four washes an average of 1 ton (2000 pounds) of clothes each year. If the standard deviation of the distribution is 187.5 pounds, find the probability that the mean of a randomly selected sample of 50 families of four will be between 1980 and 1990 pounds. Explain?

Find the probability that an observation taken from a standard normal population will be more than -2.16.

The mean of a normal probability distribution is 500; the standard deviation is 10. About 68% of the observations lie between what two values? About 95% of the observations lie between what two values? Practically all of the observations lie between what two values?

A physical fitness association is including the mile run in its secondary-school fitness test. The time for this event for boys in secondary school is known to possess a normal distribution with a mean of 450 seconds and a standard deviation of 40 seconds. Find the probability that a boy takes between 380 and 425 seconds.

According to a recent survey, the salaries of assistant professors have a mean of  $40,756  and a standard deviation of  $7500 . Assuming that the salaries of assistant professors follow a normal distribution, find the proportion of assistant professors who earn at most  $45,000 . Round your answer to at least four decimal places.

An elevator has a weight capacity of 2000 pounds. Assume the weights of us men have a mean of 190 with a standard deviation of 25 pounds. If 10 men enter the elevator; what is the probability the elevator will be over capacity?

An individual golfer's scores have a mean of 90.4 and a standard deviation of 5.3. What is the probability that the golfer will score higher than 95 in the next round?

Facebook provides a variety of statistics on its Web site that detail the growth and popularity of the site. On average, 28 percent of 18 to 34 year olds check their Facebook profiles before getting out of bed in the morning. Suppose this percentage follows approximately a normal distribution with a standard deviation of five percent. Find the probability that the percent of 18 to 34-year-olds who check Facebook before getting out of bed in the morning is at least 30.