AP Psych: Standard Deviation and Percentile Range

Normal Distribution

the arrangement of data values that cluster around the middle of the data values where the mean is located; depicted by a bell curve

negatively skewed

the characteristic of a frequency distribution in which the bulk of the data is to the right and the tail points to the left; the mode is always the highest point, the median is pulled to the left, and the mean is pulled to the left by outliers

positively skewed

the characteristic of a frequency distribution in which the bulk of the data is to the left and the tail points to the right; the mode is the highest point, the median is between the mean and mode, and the mean is pulled to the right by outliers

standard deviation

the distance of the values in a data set from the mean of all values in the data set

small deviation

the condition in which data values are all squished closer to the mean

large deviation

the condition in which data values are more spread out away from the mean

z-scores

the measure of the distance of a score from the mean in units of standard deviation

0.1%

the percentage of people between 0 and the z-score -3

2.1%

the percentage of people between the z-scores -3 and -2

13.6%

the percentage of people between the z-scores -2 and -1

34.1%

the percentage of people between the z-scores -1 and 0

34.1%

the percentage of people between the z-scores 0 and 1

13.6%

the percentage of people between the z-scores 1 and 2

2.1%

the percentage of people between the z-scores 2 and 3

0.1%

the percentage of people above the z-score 3

99%

the percentage of people between the z-scores -3 and 3

95%

the percentage of people between the z-scores -2 and 2

68%

the percentage of people between the z-scores -1 and 1

0.13%

the percentile of the value with a z-score of -3

2.28%

the percentile of the value with a z-score of -2

15.87%

the percentile of the value with a z-score of -1

50%

the percentile of the value with a z-score of 0

84.13%

the percentile of the value with a z-score of 1

97.72%

the percentile of the value with a z-score of 2

99.87%

the percentile of the value with a z-score of 3