Personality Research Methods: Correlation and Reliability
Measuring personality variables What is a variable? What kinds of variables are there? Categorical variables (examples: gender, political affiliation) Continuous variables (height, weight) How can we measure an aspect of personality as a variable? Psychometrics (psyche – mind, metric – measure): an applied branch of psychology that deals with psycho-logical measurement The most commonly used approach to study human personality: the self-report questionnaire measure
I am socially somewhat awkward. Personality Inventory Please read the following items and decide how well they describe your personality. Respond to each according to the following list of alternatives: a. very much unlike me b. somewhat unlike me c. somewhat like me d. very much like me I am socially somewhat awkward. I don’t find it hard to talk with strangers I feel tense when I’m with people I don’t know well. When conversing I worry about saying something dumb. I feel nervous when speaking to someone in authority. I am often uncomfortable at parties and other social functions. I feel inhibited in social situations. I have trouble looking someone right in the eye. I am more shy with members of the opposite sex.
Correlating variables What is a variable? What kinds of variables are there? Categorical variables (examples: gender, political affiliation) Continuous variables (height, weight) Correlating two variables Measure the two variables (X and Y) as accurately as you can Plot the variables as X-Y coordinates on a two-dimensional space Examine the shape of the “scatterplot” to estimate the size and “direction” of the correlation Compute the correlation coefficient using the correct mathematical formula (or let the computer do it for you)
Standard scores in a normal distribution
NAME HEIGHT (X) WEIGHT (Y) Allport, Allen 69 175 Bimiup, Scotty 68 159 Brewer, Joseph 71 177 Derrickson, Derek 150 Dorman, Carlton 67 162 Horne, Karyn 65 134 Ingram, Irene 64 121 James, Jocelyn 125 Jones, Ernie 158 Lang, Fred 161 Kelly, Christine 63 119 Lime, Nora 128 etc.
Reliability in personality measurement Reliability (consistency of measurement, or agreement) Internal consistency Item-to-total correlation Split-half reliability Cronbach’s alpha Parallel forms reliability Inter-observer reliability Test-retest reliability
I am socially somewhat awkward. Personality Inventory Please read the following items and decide how well they describe your personality. Respond to each according to the following list of alternatives: a. very much unlike me b. somewhat unlike me c. somewhat like me d. very much like me I am socially somewhat awkward. I don’t find it hard to talk with strangers I feel tense when I’m with people I don’t know well. When conversing I worry about saying something dumb. I feel nervous when speaking to someone in authority. I am often uncomfortable at parties and other social functions. I feel inhibited in social situations. I have trouble looking someone right in the eye. I am more shy with members of the opposite sex.
Reliability in personality measurement Reliability (consistency of measurement, or agreement) Internal consistency Item-to-total correlation Split-half reliability Cronbach’s alpha Parallel forms reliability Inter-observer reliability Test-retest reliability
Item-to-total correlations SHY1 SHY2 SHY3 SHY4 SHY5 SHY6 SHY7 SHY8 SHY9 SHY .68 .64 .67 .65 .73 .75 .57 .61
Reliability in personality measurement Reliability (consistency of measurement, or agreement) Internal consistency Item-to-total correlation Split-half reliability Cronbach’s alpha Parallel forms reliability Inter-observer reliability Test-retest reliability
Reliability in personality measurement Reliability (consistency of measurement, or agreement) Internal consistency Item-to-total correlation Split-half reliability Cronbach’s alpha Parallel forms reliability Inter-observer reliability Test-retest reliability
Reliability (internal consistency) Cronbach’s alpha = Reliability (internal consistency) Cronbach’s alpha = .83 Factor pattern Factor 1 SHY1 .69 SHY2 .62 SHY3 .67 SHY4 .66 SHY5 .65 SHY6 .75 SHY7 .78 SHY8 .54 SHY9 .58
Reliability in personality measurement Reliability (consistency of measurement, or agreement) Internal consistency Item-to-total correlation Split-half reliability Cronbach’s alpha Parallel forms reliability Inter-observer reliability Test-retest reliability