Normal Distributions

What percent of a normal distribution lies outside of ±3 standard deviations?

• 99.7%

• .15%

• .3%

• 100%

The shelf life of a particular dairy product is normally distributed with a mean of 12 days and a standard deviation of 3 days. About what percent of the products last between 12 and 15 days?

• 68%

• 99.7%

• 95%

• 34%

The speeds of cars on the highway have a mean of 95 km/h with a standard deviation of 5 km/h. What percentage of cars averaged less than 85 km/h?

• .15%

• 2.35%

• 2.5%

• 18.5%

The mean life of a tire is 30 000 km. The standard deviation is 2000 km. 68% of all tires will have a life between ______km and ______km.

• 26000 and 34000

• 28000 and 32000

• 24000 and 34000

• 22000 and 36000

A sampling distribution for means has a mean of 18 and a standard deviation of 3.0 when the sample size is n = 49. Calculate the standard error?

• 3/49

• 3/7

• 1/6

• 6

The Floppy Disk Company makes 3.5 inch floppy disks (mean) for disk drives that are 3.7 inches wide. The size of a manufactures disk is normally distributed with a standard deviation of 0.1 inches. The company manufactures 1000 disks every hour. In one hour, how many disks would you expect to be between 3.4 inches and 3.7 inches?

• 34

• 135

• 68

• 815

The distribution above is normal. What percent lies below the curve?

• 68%

• 95%

• 99.7%

• 100%

The distribution above is normal. What percent lies between ±3 standard deviations?

• 68%

• 95%

• 99.7%

• .3%

A line up for tickets to a local concert had an average (mean) waiting time of 20 minutes with a standard deviation of 4 minutes. If 2000 ticket buyers were in line, how many of them would expect to wait for less than 16 minutes?

• 320

• 1550

• 100

• 30

What is the value of the mean on this Normal Curve?