Normal Probability Distributions

A manufacturer contracts to supply ball bearings with diameters between 24.60mm and 25.4mm. Product analysis indicates that the ball bearings manufactured have diameters that are normally distributed with a mean of 25.10mm and a standard deviation of .20mm. What percentage of ball bearings fail to satisfy the contract specifications?

• 92.7%

• 7.3%

• 48.2%

• 33.2%

Between what two standard deviations of a normal distribution lies 68% of the data?

• one below and one above

• two below and two above

• two below and zero

• zero and two above

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? (You may need to draw and label a normal curve.)

• 1084 to 1216 pounds 

• 1106 to 1150 pounds 

• 1106 to 1194 pounds 

• 1128 to 1172 pounds

This data is normally distributed. What percent of the data is in the shaded region?

• 68%

• 95%

• 99.8%

• 50%

This data is normally distributed. What percent of the data is in the shaded region?

• 68%

• 32%

• 16%

• 50%

This data is normally distributed. What percent of the data is in the shaded regions?

• 5%

• 95%

• 2.5%

• 50%

This data is normally distributed.  What percent of the data is in the shaded region?

• 5%

• 95%

• 2.5%

• 50%

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 below the mean. (You may need to draw and label a normal curve.)

• 60

• 475

• 45

• 9500

The speeds of cars on the highway have a mean of 95 km/h with a standard deviation of 5 km/h. What percentage of cars averaged less than 85 km/h? (You may need to draw and label a normal curve.)

• .15%

• 2.35%

• 2.5%

• 18.5%

Which set of exam data better represents a normal distribution?

• Exam 2

• Exam 1

• Neither

• Both