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Measuring Subjective P robability in the Context of Medication R isks Niels Haase , Frank Renkewitz & Cornelia Betsch University of Erfurt (Germany). Measures of Subjective Probability. 7-Point Rating Scale. 11-Point Rating Scale. Visual Analog Scale. - PowerPoint PPT Presentation
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Measuring Subjective Probability in the Context of Medication RisksNiels Haase, Frank Renkewitz & Cornelia BetschUniversity of Erfurt (Germany)
Haase, Renkewitz & Betsch: Measuring Subjective Probability 221st Annual Conference18-20 June 2012 ETH Zurich
Measures of Subjective Probability
7-Point Rating Scale
11-Point Rating Scale
Visual Analog Scale
Haase, Renkewitz & Betsch: Measuring Subjective Probability 321st Annual Conference18-20 June 2012 ETH Zurich
Measures of Subjective Probability
Frequency Format
Percent Format
Haase, Renkewitz & Betsch: Measuring Subjective Probability 421st Annual Conference18-20 June 2012 ETH Zurich
Measures of Subjective Probability
• Differences between scales– Resolution– Verbal vs. numeric
• Evaluative criteria– Usability– Test-retest reliability– Subjective confidence in judgment– Behavior prediction
Haase, Renkewitz & Betsch: Measuring Subjective Probability 521st Annual Conference18-20 June 2012 ETH Zurich
Research Question & Design
• How do these scales perform when objective probabilities have been learned?
• SensitivityIndividual correlation between objective and subjective probabilities
• Context DependencyDifferentiation between ranges of probability
Objective Probabilities
Subjective Probability Judgment
Objective Probabilities
etc.(4 Levels of Probability)
Haase, Renkewitz & Betsch: Measuring Subjective Probability 621st Annual Conference18-20 June 2012 ETH Zurich
Hypotheses
• Rating scales’ disadvantage due to low resolution and vague category quantifiers
• Visual analog scale’s disadvantage due to difficulties in its use
• H1: Numeric scales show higher sensitivity than the visual analog scale and the rating scales.
• H2: Rating scales and the visual analog scale will be more context-dependent.
Haase, Renkewitz & Betsch: Measuring Subjective Probability 721st Annual Conference18-20 June 2012 ETH Zurich
Independent Variables
• 5 Scale Formats (between)
• 2 Ranges of probability (between):2%, 5%, 10%, 20%
vs. 42%, 45%, 50%, 60%
• Mode of presentation (within):SequentialGraphical (control)
Haase, Renkewitz & Betsch: Measuring Subjective Probability 821st Annual Conference18-20 June 2012 ETH Zurich
Sequential Presentation
Haase, Renkewitz & Betsch: Measuring Subjective Probability 921st Annual Conference18-20 June 2012 ETH Zurich
Sequential Encoding: Sensitivity
Haase, Renkewitz & Betsch: Measuring Subjective Probability 1021st Annual Conference18-20 June 2012 ETH Zurich
Sequential Encoding: Sensitivity
Low Range of Probabilities: 2%-20% High Range of Probabilities: 42%-60%
Haase, Renkewitz & Betsch: Measuring Subjective Probability 1121st Annual Conference18-20 June 2012 ETH Zurich
Sequential Encoding: Context Dependency7-point rating scale Percent format
42%20% 42%20%
Haase, Renkewitz & Betsch: Measuring Subjective Probability 1221st Annual Conference18-20 June 2012 ETH Zurich
• All scales were highly sensitive
• Numeric scales were generally superior
• Rating and visual analog scales were context dependent
• Differences between scales are reduced when encoding is more error-prone
Summary: Sequential Encoding
Haase, Renkewitz & Betsch: Measuring Subjective Probability 1321st Annual Conference18-20 June 2012 ETH Zurich
Probability of 42%:
Graphical Presentation
Haase, Renkewitz & Betsch: Measuring Subjective Probability 1421st Annual Conference18-20 June 2012 ETH Zurich
Sequential Encoding vs. Graphical Encoding
Haase, Renkewitz & Betsch: Measuring Subjective Probability 1521st Annual Conference18-20 June 2012 ETH Zurich
Graphical Encoding: Sensitivity
Haase, Renkewitz & Betsch: Measuring Subjective Probability 1621st Annual Conference18-20 June 2012 ETH Zurich
Graphical Encoding: Sensitivity
Low Range of Probabilities: 2%-20% High Range of Probabilities: 42%-60%
Haase, Renkewitz & Betsch: Measuring Subjective Probability 1721st Annual Conference18-20 June 2012 ETH Zurich
Graphical Encoding: Context Dependency7-point rating scale Percent format
42%20% 42%20%
Haase, Renkewitz & Betsch: Measuring Subjective Probability 1821st Annual Conference18-20 June 2012 ETH Zurich
• Altogether higher sensitivity
• Differences between measures remain the same, numeric formats superior
• Reduced context dependency
• No effect of range, i.e. encoding difficulty
Summary: Graphical Encoding
Haase, Renkewitz & Betsch: Measuring Subjective Probability 1921st Annual Conference18-20 June 2012 ETH Zurich
Experiment 2: Effect of encoding error
• Encoding more error-prone– 5 outcomes within 1 sequence– Shorter inter-stimulus time– 3 repeated measurements
• 2 Scale formats (between)7-point rating scale vs. Percent format
• 2 Ranges of probability (within):10%, 20%, 30%, 40%, 50% vs. 50%, 60%, 70%, 80%, 90%
Haase, Renkewitz & Betsch: Measuring Subjective Probability 2021st Annual Conference18-20 June 2012 ETH Zurich
Experiment 2: Sensitivity
Small Probabilities: 10%-50%
Large Probabilities: 50%-90%
Haase, Renkewitz & Betsch: Measuring Subjective Probability 2121st Annual Conference18-20 June 2012 ETH Zurich
Experiment 2: Context Dependency7-point rating scale Percent format
10% 20% 30% 40% 50% 50% 60% 70% 80% 90%Objective Probabilities
10% 20% 30% 40% 50% 50% 60% 70% 80% 90%Objective Probabilities
Small Probabilities: 10%-50%
Large Probabilities: 50%-90%
50% 50% 50% 50%
Haase, Renkewitz & Betsch: Measuring Subjective Probability 2221st Annual Conference18-20 June 2012 ETH Zurich
• Different scale formats vary in sensitivity with numeric measures generally faring the best
• Sensitivity also varies as a function of error in infomation at the time of judgment
• Scale characteristics (e.g. resolution) become less important with increasing error
• Context dependency increases with increasing error
• In the realm of probabilities rating scales are not suitable for between-subjects research
Conclusions & Implications
Haase, Renkewitz & Betsch: Measuring Subjective Probability 2321st Annual Conference18-20 June 2012 ETH Zurich
Thank you.
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