Measures of dispersion

tell us how spread or dispersed the data are.
1. indicate the spread or variety of people’s measurements in a distribution.
  1. Low dispersion
    1. values are similar
  2. High dispersion
    1. wide range of different values
Range
1. highest no/- lowest no
2. use of range is limited, because it tells us nothing about how the data between these two extremes are spread.
Percentile
1. divide the data into 100 equal parts with equal numbers of observations in each part.
2. help us to provide information about the location of a score in respect to other scores.
3. score at or below a certain percentage of scores lying in a distribution
4. Quartiles
  1. sets of values that divide the distribution into four parts such equal number of observations in each part
  2. Q1
    1. 25%
      1. lower quartile
  3. Q2
    1. 50%
      1. median
  4. Q3
    1. 75%
      1. upper quartile
IQR
1. is the companion to the median.
2. indicates the range of values spanned by the middle 50% of the observations
3. Q3-Q1
Standard deviation
1. the companion to the mean.
2. indicates the average distance or amount, by which each observation differs from the mean.
  1. descriptive statistic that is the most commonly used measure of dispersion or spread
  2. denoted by σ, in the population and SD or s in the sample
  3. used with the mean to describe the distribution of observations.
    1. most widely used measure of dispersion, particularly with interval and ratio level data

Resource summary

	Created by shirley.ha over 11 years ago