Section 3.4 Summary

1. In this section, we learned about measures of relative position, which tell us the position that a particular data value holds relative to the rest of the data set. The -score indicates how many standard deviations a particular data value is from the mean. The -score equals the data value minus the mean, divided by the standard deviation. We may also calculate a data value, given its -score.
2. An outlier is a value that is very much greater than or less than the mean. An outlier can be identified when its -score is less than 23 or greater than 3.
3. The th percentile of a data set is the value at which percent of the values in the data set are less than or equal to this value. The percentile rank of a data value equals the percentage of values in the data set that are less than or equal to that value.
4. Quartiles divide the data set into approximately equal quarters. The interquartile range (IQR) is a measure of spread found by subtracting the frst quartile from the third quartile.