Welcome to MM570 Applies Statistics for Psychology Unit 2 Seminar Dr. Bob Lockwood

Measures of Central Tendency: The Mean Sum of all the scores divided by the number of scores Mean of 7,8,8,7,3,1,6,9,3,8 ΣX = = 60 N = 10 Mean = 60/10 = 6

The Mean Mean of the distribution of the number of dreams during a week for 10 students.

Measures of Central Tendency: The Mode Most common single number in a distribution Mode of 7,8,8,7,3,1,6,9,3,8 = 8 Measure of central tendency for nominal variables

The Mode The mode as the high point in a distribution’s histogram, using the example of the number of dreams during a week for 10 students.

Measures of Central Tendency: The Median The middle score when all scores are arranged from lowest to highest Median of 7,8,8,7,3,1,6,9,3, median Median is the average (mean) of the 5 th and 6 th scores, so the median is 7

Measures of Central Tendency Types of Data

Measures of Variability: The Variance The average of each score’s squared difference from the mean Steps for computing the variance: 1. Subtract the mean from each score 2. Square each of these deviation scores 3. Add up the squared deviation scores 4. Divide the sum of squared deviations by the number of scores

Measures of Variability: The Variance Formula for the variance:

Measures of Variability: The Standard Deviation Most common way of describing the spread of a group of scores Steps for computing the standard deviation: 1.Figure the variance 2.Take the square root [Hint: I use SPSS]

Measures of Variability: The Standard Deviation Formula for the standard deviation:

Table 2-4: Figuring the Variance and Standard Deviation for Number of Social Interactions during a week for 94 College Students (page 48) Number of Interactions- Mean number of Interactions = Deviation Score Squared Deviation Score = = = = = = = = ∑: 0.00∑: 12,406.44

Controversies and Limitations: The Tyranny of the Mean Knowledge about the individual case is lost when taking averages Qualitative research methods e.g., case studies, ethnography

Using SPSS Mean, Median, Mode, Variance and Standard Deviation

SPSS Numerical Descriptors 1

SPSS Numerical Descriptors 2

SPSS Numerical Descriptors 3

SPSS Descriptive Statistics – Descriptives

QUESTIONS??