STATS: Central Tendencies, Frequency and Percentages

mode

Category or score that occurs with the greatest frequency in a distribution of scores in a data set

what is mode acceptable for

nominal-level data which are not continuous and cannot be ranked, compared or subjected to mathematical operations

bimodal

two scores occur more frequently than the others

multimodal

more than two modes

median

Score that lies in the middle of a rank-ordered list of values of a distribution

if a distribution is odd

the median is the middle score

if a distribution is even

the median is half of the sum of 2 humbers

What is the most precise measure of central tendency for ordinal level data and for non normally distributed or skewed interval or ratio level data

median

mean

Arithmetic average of all scores in a sample

• The sum of all scores divided by the total number of scores

what is the most accurate measure of central tendency for normally distributed data measured at the interval and ratio level

mean

in a normal distribution the…

mean, median and mode are essentially equal

Mean is sensitive to

extreme scores called outliers

outlier

a value in a sample data set that is unusually low or unusually high in the context of

the rest of the sample data

If outliers are present

The mean is often affected, and the median might be the measure of choice for central tendency

median formula

(MD)= [ (N+1) divided by 2] h (the score)

• N = number of scores

mean formula

X= Ex divided by N

• Ex: raw sum of the scores in a study

• N sample size or number of scores in the study

mode formula

just the most common number