Rating Scale Examples

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Rating Scale Examples
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A helpful resource

• http//winsteps.blogspot.com/

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Rasch Property of Invariance

• Item difficulty measure should remain constant no
  matter the population taking the assessment. If
  an item difficulty measure is different for two
  groups of students, that item is said to exhibit
  Differential Item Functioning (DIF).
• As defined by Clauser and Mazor (1998),
  Differential item functioning is present when
  examinees from different groups have differing
  probabilities of or likelihoods of success on an
  item (p. 31).
• With the Rasch model, each examinee has ability,
  and each item has difficulty. If DIF exists, item
  difficulty for the reference and focus groups
  will be different.
• The comparison of difficulty for the focus and
  reference groups can be calculated from all, or
  any convenient subset, of the reference and focus
  groups (Linacre Wright, 1987, p. 11).

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Bias

• measuring persons unfairly based on race, sex, or
  cultural background
• Is an item that exhibits DIF biased?
• For a couple of examples
• http//www.rasch.org/memo22.htm
• http//www.rasch.org/memo25.htm

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Figure Skating Example

• http//www.rasch.org/rmt/rmt154a.htm
• http//www.rasch.org/rmt/rmt102j.htm
• http//www.niu.edu/pubaffairs/RELEASES/2002/feb/sk
  ating.shtml