Statistics 1.3 Measures of Central Tendency

Skewed Left

Mean < Median

Symmetric

Mean = Median

Skewed Right

Mean > Median

arithmetic mean

computed by determining the sum of all the values of the variable in the data set and dividing by the number of observations

population mean (μ)

computed by using all the individuals in the population -this is a parameter

sample mean (x-bar)

computed by using all the individuals in the sample data -this is a statistic

mode

is the most frequent observation of the variable that occurs in the data set (an observation is not the mode just because it repeats, but it is the one that occurs the MOST) - if no observation occurs more than once, the data has NO mode - it is possible for a set of data to have more than one mode

median (M)

is the value that lies in the middle of the data when arranged in ascending order

N

population size

n

sample size