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Why does the Wilcoxon signed-rank test ignore zero differences between pairs?

hard📝 Conceptual Q10 of 15
SciPy - Statistical Tests

Why does the Wilcoxon signed-rank test ignore zero differences between pairs?

AZero differences provide no information about direction or magnitude
BZero differences violate test assumptions
CZero differences inflate the test statistic
DZero differences cause errors in rank calculation
Step-by-Step Solution
Solution:

  1. Step 1: Understand zero differences meaning

    Zero difference means no change between paired observations.

  2. Step 2: Reason why they are ignored

    They do not indicate direction or magnitude, so they don't affect ranks or test statistic.

  3. Final Answer:

    Zero differences provide no information about direction or magnitude -> Option A

  4. Quick Check:

    Zero differences excluded as they add no info [OK]
Quick Trick: Zero differences don't affect signed ranks, so ignored [OK]
Common Mistakes:
MISTAKES
  • Thinking zeros cause errors
  • Assuming zeros bias results
  • Including zeros in rank sums

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