STAT151 Chapter Notes - Chapter 5: Standard Deviation, Frequency Distribution, Normal Distribution

• School: University of Alberta
• Department: Statistics
• Course: STAT151
• Professor: Omar Rivasplata

Document Summary

To standardize a value, we subtract the mean and then divide this difference by the standard deviation. The values are called standardized values, and are commonly denoted with the letter z. Z-scores measure the distance of a value from the mean in standard deviations o. For example, a z-score of 2 means that particular data value is two standard deviations from the mean. Changing the original variable"s units will not affect a z-score. Finding z-scores is a two-part process; first, the data is shifted by subtracting the mean, then it is rescaled by dividing by the standard deviation. When we shift the data by adding or subtracting a constant to each value, all measures of position (centre, percentiles, min, max) will increase or decrease by the same constant. Adding or subtracting a constant to every data values adds or subtracts the same constant to measure of position, but leaves measure of spread unchanged.