EC255 Chapter Notes - Chapter 3: Average Absolute Deviation, Standard Deviation, Level Of Measurement
Document Summary
Provide information about the center or middle part of a numbers. There may be no mode or several modes group of. Median: middle value in an ordered array of numbers. Mean: the most common measure of central tendency. Mean: the sum of values divided by the number of values. Used to indicate how much are the observations mean. Average of the absolute deviations from the mean (no negative numbers) Average of the squares of deviations from the mean. Use the square root of the variance to have intuitive interpretation standard deviation. Same idea as population variance, but related to the sample. Thus we lost one degree of freedom s2 = (x - m)2. The standard deviation can be used to compare the variability of several distributions. If the histograph is bell shaped we say that: 68% of all observations fall within 1 standard deviation of the mean. 95% of all observations fall within 2 stdev of the mean.
