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.

The average waist size for teenage males is 29 inches with a standard deviation of 2 inches. 
If waist sizes are normally distributed, determine the z-score of a teenage male with a 33 inch waist.  

• 2
• 1
• -2
• -1

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%

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

• 2.5
• -2.5
• 5.2
• -5.2

What is the z-score for the mean?

• -1

• +1

• 0

• It doesn't have one!

If I have a positive z-score, I scored ABOVE or BELOW the mean?

• ABOVE

• BELOW

Brian scored an 80% on a Chemistry Exam. The average on the exam was a 68%, with a standard deviation of 5%. What is Brian's z-score?

• 2.4

• -2.4

• 1.1

• -1.1

Joanne's Z-score is -1.5. What does this mean?

• She didn't take the test yet.

• She scored 1.5 standard deviations below the average.

• She did better than most people.

• No clue

1) What will be the miles per gallon for a Toyota Camry when the average mpg is 23, it has a z value of 1.5 and a standard deviation of 2?

• 25

• 20

• 26

• 68