normal distribution ap psych

empirical rule of uniform percentages

• 68% of data falls within 1 st. dev.

• 95% of data falls within 2 st. devs

• 99% of data falls within 3 st. devs

1 standard deviation

34.1%

2 standard deviations

13.6%

3 standard deviations

2.1%

negatively skewed (skewed left)

mean < median

positively skewed (skewed right)

mean > median

z score

how many standard deviations the data is from the mean

z = 0

mean

normal distribution

symmetrical: mean = median = mode

negative z score

below the mean

positive z score

above the mean