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Measurement The process whereby individual instances within a defined population are scored on an attribute according to rules Usually given a numeric score Measurement is meant to make comparisons among individual cases easier, more precise and more accurate

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Measurement The easiest examples to understand involve the measurement of physical properties of objects Height Weight Volume Measuring intangibles such as opinion, intent, beliefs, etc. is difficult and open to error

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Measurement issues Validity: does the measure actually reflect the underlying concept? Are you measuring what you intend to measure? Accuracy Reliability: does the measure perform the consistently from one occasion to another? Precision/sensitivity: how large are the differences between adjacent categories/scores? Efficiency: cost versus value of information

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Self-report measures Memory Forgetting Bias Social desirability Respondent may believe a given answer is more acceptable to the researcher Knowledge Respondents may not know or understand the ideas Often, respondents will answer questions without really knowing what they are about

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Self-report measures Sensitive to mood of the respondent Sensitive to interview situation Sensitive to data collection method Internet Interview Paper and pencil

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Tests as measures Pretty much all tests of your knowledge would fall under the category of self-report measures All tests are prone to some level and type of error Many types of tests exist, each having its strengths and weaknesses Multiple-choice Fill in the answer Essay Apply the concept

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The GRE FairTest analysis FairTest analysis ETS analysis ETS analysis

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Observation Internal states are only partially reflected in observable behavior, etc. Behaviors are influenced by the situation, which may not be evaluated May know they are being watched and change their behavior Observer may engage in biased perception, interpretation, etc.

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Mechanical observation Manifest behavior may not really reflect the underlying concept you think it does Skin conductance Website hits Often intrusive to the point of being unnerving Eye tracking

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Eye Tracking Source: Max Planck Institute at: http://www.mpi.nl/world/tg/eye-tracking/eye-tracking.html

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Measurement levels Differences in measurement level refer to the kind of information conveyed in the scores individual objects receive Four levels: nominal, ordinal, interval, ratio More advanced levels provide a greater amount of information with the score they assign More advanced levels allow for more powerful statistical analysis of the data

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Nominal-level measurement Numbers are assigned to individual objects simply as a means to distinguish among them Distinction without order

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A nominal-level measure 1 2 3 4 56

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Ordinal-level measurement Scores indicate order, but not distance along some dimension The difference between a one and a two may be greater or less than the difference between a two and a three

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An ordinal-level measure Large dog Score: 3 Small dog Score: 1 Medium size dog Score: 2

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Interval-level measurement Scores indicate direction and distance Intervals are of equal sizethe difference between 1 and 2 is equal to the difference between 3 and 4 The zero point is arbitrarydoes not indicate complete absence of the attribute Many statistical analyses assume this level of measurement

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An interval-level measure

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Ratio-level measurement Scores indicate order and distance from a true zero point The units along the scale are equal Allows for calculation of the ratio of one point on the scale compared to another

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Ratio-level measures

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Scales When measuring attitudes, behaviors, etc. there is bound to be a significant amount of measurement error For reasons we will look at later, using multiple items/measures to create scores for individual objects improves the measurement of each one We call measures combining multiple items to measure a single concept scales

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Scales Each item in a scale is supposed to measure the construct of interest, but it is possible that either: The concept has more than one dimension, or The items tap into more than one concept To test for multidimensionality, statistical techniques are available Factor analysis Interitem correlations

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Scale development To improve the reliability/performance of the scale, a researcher may remove items that reduce reliability, etc. May weight items according to their factor loadings

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Humor orientation scale Response categories: 1=strongly agree, 2=agree, 3=neutral, 4=disagree, 5=strongly disagree 1. I regularly tell jokes and funny stories when I am in a group 2. People usually laugh when I tell a joke or story 3. I have no memory for jokes or funny stories 4. I can be funny without having to rehearse a joke 5. Being funny is a natural communication style with me 6. I cannot tell a joke well 7. People seldom ask me to tell stories 8. My friends would say that I am a funny person 9. People dont seem to pay close attention when I tell a joke 10. Even funny jokes seem flat when I tell them