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Chapter 5

# Chapter 5 notes

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University of Toronto Scarborough

Psychology

PSYB01H3

Connie Boudens

Fall

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Chapter 5 Measurement concepts Reliability of measures - Reliability: consistency or stability of a measure of behaviour - A reliable measure does not fluctuate from one reading to the next. If the measure does fluctuate, there is error in the measurement device - Any measure you make comprises two components (1) a true score, which is the real score of the variable, and (2) measurement error - When doing research, you can measure each person only once; you cant give the measure 50 or 100 times to discover the true score - studying behaviour using unreliable measures is a waste of time because the results will be unstable and unreplicable. - Reliability is most likely achieved when researchers use careful measurement procedures - We cant directly observe the true score and error of an actual score on the measure. But we can assess the stability of measures using correlation coefficients - A correlation coefficient is a number that tells us how strongly two variables are related to each other - Most common correlation coefficient when discussing reliability is the Pearson product-moment correlation coefficient. Pearson correlation coefficient (symbolized as r) can range from 0.00 to +1.00 and 0.00 to -1.00. A correlation of 0.00 tells us that the two variables are not related at all. The closer a correlation is to 1.00, either +1.00 or -1.00 the stronger the relationship - When the correlation coefficient is positive there is a positive linear relationship high scores on one variable are associated with high scores on the second variable - A negative linear relationship is indicated by a minus sign high scores on one variable are associated with low scores on the second variable - To assess the reliability of a measure, we will need to obtain at least two scores on the measure from many individuals. If the measure is reliable, the two scores should be very similar; a Pearson correlation coefficient that relates the two scores should be a high positive correlation Test-Retest Reliability - Test-retest reliability: assessed by measuring the same individuals at two points in time - we would have two scores for each person, and a correlation coefficient could be calculated to determine the relationship between the first test score and the retest score - For most measures the reliability coefficient should probably be at least .80 - Given that test-retest reliability involves administering the same test twice, the correlation might be high because the individual remembers how they responded the first time. Alternate forms reliability is sometimes used to avoid this problem. Alternate forms reliability involves administering two different forms of the same test to the same individual at two points in time www.notesolution.com

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