Essay

In Birnbaum's (1999) classic study demonstrating the limitations of between-subjects designs, participants rated either the number 99 or the number 221221 on a scale. Describe the experimental design and the specific findings of this study, and explain the cognitive mechanism that led to the paradoxical rating results.

Question: In Birnbaum's (1999) classic study demonstrating the limitations of between-subjects designs, participants rated either the number 99 or the number 221221 on a scale. Describe the experimental design and the specific findings of this study, and explain the cognitive mechanism that led to the paradoxical rating results.

Sample answer: Birnbaum (1999) used a between-subjects design where one group of participants rated the number 99 and a separate group rated the number 221221 on a size scale. Paradoxically, the group rating 99 judged it as mathematically 'larger' than the group rating 221221. This occurred because the between-subjects design lacked a direct within-subjects comparison context. Consequently, participants spontaneously compared the single digit 99 to other single-digit numbers (making it seem large) and 221221 to other three-digit numbers (making it seem small), which skewed their relative size judgments.

Key points:

  • A between-subjects design was used, assigning participants to separate rating groups.
  • Participants evaluated either the number 99 or the number 221221 on a size scale.
  • The group rating 99 paradoxically rated it as mathematically 'larger' than the group rating 221221.
  • The lack of context in the between-subjects design led participants to compare 99 to single-digit numbers and 221221 to three-digit numbers.

Rubric: Grading Rubric: - Mentions that a between-subjects design was used (separate groups for each number rating). - Identifies the numbers rated (99 and 221221). - Identifies the paradoxical finding: 99 was rated as larger than 221221. - Explains the cognitive mechanism: lack of context led participants to spontaneously compare 99 to single-digit numbers and 221221 to three-digit numbers.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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