Class Notes (836,069)
Psychology (2,794)
PS296 (9)
Max Gwynn (7)
Lecture 2

# PS296 Week 2C (Measures of Variability)

4 Pages
104 Views

Department
Psychology
Course
PS296
Professor
Max Gwynn
Semester
Winter

Description
PS296 Week 2C (Measures of Variability) • Also called measures of dispersion. • Indicate how spread out (dispersed) the scores in a distribution are. • Dispersion (Variability): – the degree to which individual data points are distributed around the mean • All yield numerical values, i.e., a quantification of variability. Measures of variability • Range • Variance • Sum of squares • Standard deviation Range: Calculated as the difference between the highest score and the lowest score in a data set. • Range = (Highest score - Lowest score) • advantage: simple to calculate • disadvantage: takes into account only two scores, no matter how large your data set • so, it is sensitive to all scores Deviation scores • how much each score varies (deviates) from the mean • involves deviation scores: deviation score = (x-x) • problem: sum of the deviation scores in a data set always equals 0 (within rounding error), i.e., Σ(X - X) = 0 • So the average deviation score also always equals 0 Mean absolute deviation • MAD = • Not difficult to calculate, but doesn’t have the nice statistical properties that other measures of dispersion have. • Rather than use the absolute deviation, another way of getting rid of the negative values is to square each deviation score. Sum of squares • SS = the sum of the squared deviation scores 2 • SS = Σ(X - X) • Steps: – Calculate the mean: X – Calculate the deviation scores: (X – X) – square each deviation score: (X - X) 2 2 – Sum the squared deviation scores: Σ(X - X) Variance • variance is like an average squared deviation.
More Less

Related notes for PS296
Me

OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Join to view

OR

By registering, I agree to the Terms and Privacy Policies
Just a few more details

So we can recommend you notes for your school.