Wechsler IQ bell curve

What percentage of all scores are within the 1 standard deviation above or below the mean

68%

Example of 1 standard deviation

• Imagine the mean test score is 80, and the standard deviation is 5

• 1 below: 80 - (1×5) = 75

• 1 above: 80 + (1x5) = 85

• So about 68% of students scored between 75 and 85

what percentage of all scores are within the 2 standard deviation above or below the mean

95%

Example of 2 standard deviation

• Imagine the mean test score is 80, and the standard deviation is 5

• 2 below: 80 - (2×5) = 70

• 2 above: 80 + (2×5) = 90

• So about 95% of scores are between 70 and 90

0 to 55

• Profoundly Intellectually disabled

• 0.1%

55 to 70

• Intellectually disabled

• 2%

70 to 85

• Below average

• 14%

85 to 115

• Average

• 68%

115 to 130

• Above average

• 14%

130 to 145

• Gifted

• 2%

145 to 200

• Genius

• 0.1