Lt. Flannelly et al., Comparison of forced-choice and subjective probability scales measuring behavioral intentions, PSYCHOL REP, 86(1), 2000, pp. 321-332
Three surveys compared the accuracy of predictions based on forced-choice a
nd subjective probability scales. The latter produced significantly more ac
curate election predictions and significantly reduced the percentage of und
ecided, or "Don't Know" responses, compared to forced-choice scales in all
three surveys. Analysis indicates subjective probability scales decrease sa
mpling error and confirms there is an inherent source of error in tradition
al forced-choice questions about voting intentions not attributable to samp
ling error. The results are discussed with respect to (1) sampling and meas
urement errors in forced-choice and subjective probability scales measuring
behavioral intentions, (2) their practical application, and (3) cognitive
theory, especially support theory.