This preview shows page 1. Sign up to view the full content.
Unformatted text preview: of
Observations” Measures of dispersion
• Dispersion/Variability refers to how much the scores in a distribution differ from the mean
–
–
– Variance
Standard deviation
Range Measures of dispersion: Range
Measures of dispersion: Range
• Difference between biggest and smallest score – Easy to calculate, but is only based on 2 scores
• Not very informative as it ignored most of the data Measures of dispersion: Variance
Measures of dispersion: Variance
• The sum of the squares of the deviations about the mean, divided by the number of scores minus 1
– Involves calculation if the deviation scores Variance = s 2 ∑(X − M )
=
n −1 2 Calculating the variance
Calculating the variance
1: Calculate the mean value of X s 2 ∑(X − M )
=
n −1 2 Calculating the variance
Calculating the variance
2: Calculate the deviation score separately
for each value of X s 2 ∑(X − M )
=
n −1 2 Calculating the variance
Calculating the variance
3: Square the deviation score
for each value of X s 2 ∑(X − M )
=
n −1 2 Cal...
View
Full
Document
This note was uploaded on 03/12/2013 for the course PSYC 2001 taught by Professor Mathewyoung during the Winter '11 term at Carleton CA.
 Winter '11
 Mathewyoung
 Psychology

Click to edit the document details