Normal curve 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.

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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

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CCSS.HSS.ID.A.4

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%

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The z-score represents.....

• the amount of standard deviations a data value is above or below the mean.
• the percentile the data value is above or below the mean.
• the amount of standard deviations a data value is above or below the median.
• the percent the data value is above or below the mean.

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By the way, what is standard deviation?

• good question

• how standardly something deviates

• average distance that data points are from the average

• Idk but I should probably find out pretty soon

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

• ABOVE

• BELOW

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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

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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

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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 6 days or less?

• 68%
• 34%
• 16%
• 2.5%

Pat and Chris both took a spatial abilities test (mean = 80, std. dev. = 8).  Pat scores a 76 and Chris scored a 94.  What percent of individuals would score between Pat and Chris? 

• 26.8%
• 96%
• 65.1%
• 4%