Which step describes converting data for the sign test?

Which step describes converting data for the sign test?

• A. Convert data into nominal data by subtracting one condition from the other and sign accordingly.
• B. Rank the data and compute a median difference.
• C. Compute the average difference between conditions.
• D. Determine the sample size.

Answer: (A)

The essential idea is preparing paired data for a sign test by focusing only on the direction of difference, not its size. For each participant, subtract one condition from the other and record whether the result is positive or negative. Then, convert these outcomes into two categories (plus or minus) and discard any zero differences. This turns the data into nominal data with two categories, which is exactly what the sign test analyzes: it counts how many pairs show a positive difference versus a negative one and tests whether that distribution could occur by chance. The other steps align with different approaches. Ranking and looking at a median difference is for the Wilcoxon signed-rank test, which uses the magnitude of differences as well as direction. Computing the average difference relies on the actual differences and assumes interval/ratio data. Determining the sample size is about study design, not data preparation for the test.

The essential idea is preparing paired data for a sign test by focusing only on the direction of difference, not its size. For each participant, subtract one condition from the other and record whether the result is positive or negative. Then, convert these outcomes into two categories (plus or minus) and discard any zero differences. This turns the data into nominal data with two categories, which is exactly what the sign test analyzes: it counts how many pairs show a positive difference versus a negative one and tests whether that distribution could occur by chance.

The other steps align with different approaches. Ranking and looking at a median difference is for the Wilcoxon signed-rank test, which uses the magnitude of differences as well as direction. Computing the average difference relies on the actual differences and assumes interval/ratio data. Determining the sample size is about study design, not data preparation for the test.