1. Lecture 4 Psyc 300A

2. Measures of Central Tendency
Mode: The most frequently occurring score
Median: The midpoint in an ordered set of scores. The 50th percentile.
Mean: Sum of all scores divided by the number of scores.
Which measure to use?

3. Measures of Dispersion
Range: Highest score minus lowest score.
Standard Deviation: Average amount of variability in a set of scores. Technically, the square root of variance.
Variance: Average squared deviation from the mean.

4. Formulas to Calculate the SD

5. Standard Deviation _ _ X (X – X) (X – X)2 8 +2 4 7 +1 1 6 0 0 5 -1 1
_ _
X (X – X) (X – X)2
sum
s = Sqrt (28/n-1)= 1.76

6. Using SPSS What is SPSS? Setting up a data file
Running a frequency analysis with descriptive statistics