Understanding IQ Scores and Z-Scores

The video tutorial explains how to calculate the percentage of people within certain IQ score ranges using the bell curve and z-scores. It covers the calculation of percentages for IQ scores between 85 and 115, 70 and 130, and above 130. The tutorial also discusses the concept of genius IQ scores, specifically those above 145, and how the empirical rule supports this classification.

What is the mean IQ score in a bell-shaped distribution?

• 85

• 100

• 115

• 130

What is the standard deviation of IQ scores in this distribution?

• 25

• 20

• 10

• 15

How do you calculate a z-score?

• X minus the mean over standard deviation

• X minus the mean times standard deviation

• X times the mean over standard deviation

• X plus the mean over standard deviation

What is the z-score for an IQ of 85?

• -1.00

• 2.00

• 0.00

• 1.00

What percentage of people have an IQ between 85 and 115?

• 75.00%

• 95.44%

• 68.26%

• 50.00%

What is the z-score for an IQ of 70?

• -2.00

• 0.00

• 1.00

• -1.00

What is the z-score for an IQ of 130?

• 1.00

• 3.00

• 4.00

• 2.00

What percentage of people have an IQ between 70 and 130?

• 95.44%

• 99.00%

• 75.00%

• 68.26%

What is the z-score for an IQ greater than 130?

• 1.00

• 4.00

• 2.00

• 3.00

What percentage of people have an IQ greater than 130?

• 10.00%

• 2.28%

• 15.00%

• 5.00%