Answer to Question 1
Factor analysis uses multiple correlations to determine which of the measured elements cluster together. The elements that cluster together form a factor that is named for the common theme the elements in the cluster possess. For example, if words like reticent, timid, bashful, modest, demure, self-conscious, and reserved form a statistical cluster, then this cluster, known as a factor, can be labeled shyness because shyness is the construct or theme the factor appears to represent.
Based on his factor analyses, Cattell proposed that there are 16 distinct correlated factors or what he referred to as source traits (because they each presumably tapped into the one underlying source of all personality characteristics) that constitute each person's personality. He developed the Sixteen Personality Factor (16 PF) Questionnaire to measure these dimensions.
Answer to Question 2
Moderation models assume that personality influences the strength or direction of the relationship between stress and health. Personality is an intervening variable between stress and health and can serve as an intensifier of stress or a buffer that reduces the impact of stressors. Thus, when a person encounters a potentially stressful situation, that individual's personality influences how he or she will appraise and then cope with the event. This in turn will affect that person's physiological, emotional, behavioral, and cognitive responses, which will then increase or decrease susceptibility to illness.
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