Standard Deviation and Normal Distribution

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 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 6 and 18 days?

• 68%

• 95%

• 99%

• 2.5%

What shape is another name for a normal distribution?

• Half curve

• Round curve

• Bell curve

• Square curve

50% of the females are above what height?

• 5'3"

• 5'8"

• 5'9.5"

• 5'11"

What percentage of females are between 5'3.5" and 5'6.5"?

• 16%

• 68%

• 81.5%

• 95%

The mean GPA of students in a course at UCDavis is 3.2 with a standard deviation of 0.3. What percent of students in the course have a GPA between 2.9 and 3.5?

• 81.5%

• 47.5%

• 68%

• 95%

The 40 yards sprint times for a soccer team are found to be normally distributed with a mean of 5.2 seconds and a standard deviation of 0.3 seconds.  What is the z-score for a player who runs a time of 5.6 seconds?

• -1.33

• 1.33

• 0.88

• 1.02

Between what two standard deviations of a normal distribution contain 68% of the data?

• one below and one above

• two below and two above

• two below and zero

• zero and two above

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%

μ = 70 , σ = 8 , X = 50 . Find z score

• 2.5

• -2.5

• 5.2

• -5.2