Standard Deviation and Normal Distribution

Company A has a mean of 90 and a standard deviation of 20

Company B has a mean of 75 and a standard deviation of 30.

Which company had less variation?

• Company A because the standard deviation was lower

• Company A because the mean was higher

• Company B because the standard deviation was higher

• Company B because the mean was lower

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%
• 34%
• 16%
• 2.5%

At a local high school, GPA's are normally distributed with a mean of 2.9 and standard deviation of 0.6. What percentage of students at the high school have a GPA between 2.3 and 3.5?

• 68%
• 99.7%
• 95%
• 84%

The weights of adult male beagles are normally distributed, with a mean of 25 pounds and a standard deviation of 3 pounds. A beagle is randomly selected. Find the probability that the beagle’s weight is between 23 and 26 pounds.

• 0.3694
• 0.3781
• 0.0912

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%