Psyc3128
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For which scales can a mean be calculated

For which scales can a median be calculated

For which scales can a mode be calculated?
 Nominal
 Ordinal
 Interval
 Ratio

Advantages & Disadvantages of using the mean
 easily manipulated algebraically
 reliable because it takes into account every measure of a data set
greatly affected by extreme scores

Advantages & Disadvantages of Median
 little influence by extreme scores
 reasonable estimate of the center of a distribution
may not be good to ignore extreme values

Advantages & Disadvantages of Mode
not influenced by extreme scores
 may not represent the scores
 ignores extreme values completely

How to calculate IQR?
 Find the median location (n+1)/2
 Find quartile location (ML+1)/2
 Find Q1 & Q3 (low score + QL; high  QL)
 IQR= distance btwn Q3  Q1
 Outliers: Q3+ (1.5 x IQR); Q1(1.5 x IQR)

Empirical Rule...
689599.7 within 3 standard deviations of the mean

Deviation
the difference btwn each score and the mean of the data set

Variance
single number representing the average amount of variation in a data set

Standard deviation
Measure of the spread of scores out from the mean of the sample