Normal Distributions and Confidence Intervals

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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CCSS.HSS.ID.A.4

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

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CCSS.HSS.ID.A.4

The mean baking time of an angel food cake is 41 minutes with a standard deviation of 5 minutes (normally distributed). What percent of angel food cakes take less than half an hour to bake?

• 98.61%

• 2.2%

• 1.39%

• 97.8%

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CCSS.HSS.ID.A.4

The mean number of accidents a week at a company is 6.4 with a standard deviation of 1.5.  What proportion of weeks would you expect to have more than 7 accidents?

• 0.3446
• 0.2856
• 0.4
• 0.6554

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CCSS.HSS.ID.A.4

6.5 CLT:  Red blood cell counts of women are normally distributed with a mean of 4.577 and a standard deviation of 0.382.  What percentage of women have red blood cell counts in the normal range from 4.2 to 5.4?

• 82.3%
• 77.8%
• 72.6%
• 68%

Tags

CCSS.HSS.ID.A.4

The mean life of a battery is 50 hours with a standard deviation of 6 hours. The manufacturer advertises that they will replace all batteries that last less than 38 hours. If 50,000 batteries were produced, how many would they expect to replace?

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CCSS.HSS.ID.A.4

The mean number of accidents a week at a company is 6.4 with a standard deviation of 1.5.  What proportion of weeks would you expect to have less than 5 accidents?

• 0.6915
• 0.1762
• 0.8238
• -0.93

Tags

CCSS.HSS.ID.A.4

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

Tags

CCSS.HSS.ID.A.4

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%

Tags

CCSS.HSF-LE.A.1B

Find the z-score for 48 given a mean of 50 and a standard deviation of 5.

• 2.5

• -2.5

• -0.4

• 0.4