Reverse Helmert contrast is defined as:

Reverse Helmert contrast is defined as:

• A. A contrast comparing the last condition to the mean of earlier conditions.
• B. A contrast that compares each condition to the overall mean.
• C. Another name for a difference contrast.
• D. A contrast that compares adjacent means.

Answer: (C)

Reverse Helmert contrasts compare each level to the mean of the preceding levels, so the last condition is contrasted with the mean of all earlier conditions, then the next-to-last with the mean of the levels before it, and so on. This creates a sequence of orthogonal comparisons that move backward through the treatment levels. For example, with four conditions, you’d have a contrast comparing condition D to the mean of A, B, and C; then C to the mean of A and B; and B to the mean of A. The key idea is comparing a level to the average of the earlier levels, not to the grand mean or to an adjacent level. This is different from comparing each level to the overall mean (that would be a grand-mean contrast), or from differences that focus on adjacent means (that’s a difference or adjacent-mean contrast).

Reverse Helmert contrasts compare each level to the mean of the preceding levels, so the last condition is contrasted with the mean of all earlier conditions, then the next-to-last with the mean of the levels before it, and so on. This creates a sequence of orthogonal comparisons that move backward through the treatment levels. For example, with four conditions, you’d have a contrast comparing condition D to the mean of A, B, and C; then C to the mean of A and B; and B to the mean of A. The key idea is comparing a level to the average of the earlier levels, not to the grand mean or to an adjacent level.

This is different from comparing each level to the overall mean (that would be a grand-mean contrast), or from differences that focus on adjacent means (that’s a difference or adjacent-mean contrast).