Normal Distribution, Z-Score

So, y values represent the actual, measurements that we are interested in.

• True

• False

The average waist size for teenage males is 29 inches with a standard deviation of 1.4 inch.

If waist sizes are normally distributed, estimate the proportion of teenagers who will have waist sizes greater than 31 inches?

• 92.4%

• 10.5%

• 16%

• 7.6%

Pat and Tom took a test with mean 80 and SD 9. Pat scored a 76; Tom scored a 94. Find the percent of people between their scores.

• 68.78%

• 63.29%

• 61.06%

• 34.25%

Test has a mean of 40 and a standard deviation of 10. What is the percent of people that scored above 62?

• 1.39%

• 45.34%

• 98.41%

• 22.34%

The lifetime of a particular type of car tire is normally distributed. The mean lifetime is 50,000 miles, with a standard deviation of 5,000 miles. Of a random sample of 15,000 tires, how many of the tires are expected to last for between 45,000 and 55,000 miles?

• 7,125

• 10,200

• 14,250

• 14,850

Given a mean of 75 and a standard deviation of 7, how many students out of 500 would score higher than 68?

• 11

• 12

• 420

• 250

What is the standard deviation of the distribution?

• 1010

• 20

• 60

• √20

The mean life of a tire is 30,000 km. The standard deviation is 2000 km.

Then, 68% of all tires will have a life between ___________ km and __________ km.

•  28,000 km and 32,000 km.

• 24,000 km and 34,000 km.

• 26,000 km and 34,000 km.

• 27,000 km and 31,000 km.

The distribution of heights of adult American men is approximately Normal with mean 69 inches and standard deviation 2.5 inches. Between what heights do the middle 95% of men fall? 

• 66.5-71.5

• 64-74

• 61.5-76.5

• 65-73

The normal curve is symmetrical about the mean.

• True

• False