Empirical Rule & Z-Scores

In a factory, the weight of the concrete poured into a mold by a machine follows a normal distribution with a mean of 1150 pounds and a standard deviation of 22 pounds. Approximately 95% of molds filled by this machine will hold weights in what interval? 

• 1084 to 1216 pounds 
• 1106 to 1150 pounds 
• 1106 to 1194 pounds 
• 1128 to 1172 pounds

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CCSS.HSS.ID.A.4

A national achievement test is administered annually to 3rd graders. The test has a mean score of 100 and a standard deviation of 15. If Jane's z-score is 1.20, what was her score on the test?

• 82
• 88
• 100
• 118

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CCSS.HSS.ID.A.4

1.  Which best describes the shaded part of this normal distribution graph?  

• All data that is one or higher.
• All data that is one or more standard deviations above the mean.
• All data that is between 1 and 3.
• All data that is above the mean.

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CCSS.HSS.ID.A.4

Scores on a certain standardized test have a mean of 500, and a standard deviation of 100. How common is a score between 600 and 700? Calculate the probability. 

• 2.5%
• 2.35%
• 16%
• 13.5%

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CCSS.HSS.ID.A.4

At a local high school, GPA's are normally distributed with a mean of 2.9 and standard deviation of 0.6. What percentage of students at the high school have a GPA between 2.3 and 3.5?

• 68%
• 99.7%
• 95%
• 84%

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CCSS.HSS.ID.A.4

At a local high school, GPA's are normally distributed with a mean of 2.9 and standard deviation of 0.6. What is the GPA of the highest 2.5% of the students?

• 4.1 
• 4.1 or higher
• 4.7
• 4.5 or higher

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CCSS.HSS.ID.A.4

A test is given that has a mean of 70 and a standard deviation of 13. If a student's Z-score is +1, the student's score before conversion was:

• 70
• 83
• 57
• Cannot be determined from the information given.

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CCSS.HSS.ID.A.4

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 mean temperature in Glens Falls for the month of February is 23 degrees with a standard deviation of 4.2 degrees.  What is the z-score for a temperature of 17 degrees?  

• 1 
• 1.43
• -1.43
• 11.5

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CCSS.HSS.ID.A.4

The normal curve is symmetrical about the mean.

• True
• False