Normal Distribution and Z-Scores

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.

What shape is a normal distribution curve?

• Half curve
• Round curve
• Bell curve
• Square curve

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%

Find the cumulative area that corresponds to a z-score of 1.25. 

• 0.89
• 0.01
• 0.79
• 0.12

The monthly phone bills in a city are normally distributed with a mean of 30$ and a standard deviation of 12$. Find the x-value that correspond to z-scores of 3.17. 

• $1.80 
• $68.04
• $32.76

Annual U.S. per capita orange use: μ =11.4 lb, σ = 3lb. What annual per capita use of oranges represents the 10th percentile?

• 7.56 lbs
• 13.42 lbs
• 8.29 lbs 
• 9.38 lbs

In a survey of men in the United States (ages 20-29), the mean height was 69.6 inches with a standard deviation of 3.0 inches. Find the minimum height in the top 22%.

• 69.37 in 
• 67.58 in 
• 73.12 in 

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

• 2.5
• -2.5
• 5.2
• -5.2

Find the area of the shaded region. 

• 0.16
• 0.84
• 0.68
• 0.34

Find the area of the shaded region. 

• 0.16
• 0.84
• 0.68
• 0.34