In a line plot of means across ordered conditions, a cubic trend is indicated by how many changes in direction?

• A. One change in direction
• B. Two changes in direction
• C. Three changes in direction
• D. Four changes in direction

Answer: (B)

When you look at means across ordered conditions, the shape of the line reveals how the trend changes direction over the sequence. A straight line has no turning points, indicating a linear trend. A curve with one bend shows one change in direction, which corresponds to a quadratic trend. A cubic trend, however, can produce two bends, creating an S-shaped pattern that goes up, then down, then up (or the opposite). So a cubic trend is indicated by two changes in direction in the line plot. The other options don’t fit: zero changes means linear, one change means quadratic, and four changes would exceed what a cubic can produce.