Normal Distributions

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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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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A grading scale is set up for 1000 students’ test scores. It is assumed that the scores are normally distributed with a mean score of 75 and a standard deviation of 15. Calculate the score that lies -2 standard deviation from the mean.

• 60

• 475

• 45

• 9500

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What percent of a normal distribution lies outside of ±3 standard deviations?

• 99.7%

• .15%

• .3%

• 100%

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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 between 12 and 15 days?

• 68%

• 99.7%

• 95%

• 34%

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CCSS.HSS.ID.A.4

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

• 2.5
• -2.5
• 5.2
• -5.2

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CCSS.HSS.ID.A.4

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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The normal curve is symmetrical about the mean.

• True
• False

Between what two standard deviations of a normal distribution lies 95% of the data?

• one below and one above

• two below and two above

• two below and zero

• zero and two above

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