Probability and Z-Scores

The sign of the z-score indicates whether the location is above(positive) or below(negative) the mean.

• True

• False

Find the z-score value corresponding if the location is below the mean by 2 standard deviations

• +2.00

• -2.00

• +1.25

• -1.00

Find the z-scores value corresponding if the location is above the mean by 1/2 standard deviations

• -0.50

• +1.00

• +0.50

• -1.00

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.

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%

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%

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.

A z-score tells you...

• the standard deviation of a sampling distribution.
• the original raw score on which it is based.
• if the distribution it comes from is normal.
• how many standard deviations away from the mean a score lies.

Find the area under the standard normal curve to the right of z = -2.67.

• 0.0869
• 0.9962
• 0.0008
• 0.1234

Find the area under the normal distribution curve between a z=-1.26 and z=.57. 

• 0.0047
• 0.9204
• 0.6119
• 0.4981