PS296 Lecture Notes - Lecture 3: Standard Deviation, Interquartile Range
Range:
-the distance from the lowest score to the highest score in a dataset
-range is equal to the highest score – the lowest score
-outlier: an extreme score in a distribution
Interquartile range:
-the range of the middle 50% of data
-ignores extreme datapoints at the tails of distribution
-aka trimmed samples and statistics
-remove top and bottom 25% of data
Can divide graph into 4 parts
-middle 50%
-25th percentile (quarter to the left of the middle)
-75th percentile (quarter to the right of the middle)
Standard Deviation
-measure or index of the amount of variability that is equal to the square root of the
variance
-the average of deviations of each score from the sample mean
-SD is the most common measure of spread