Table 1.
Means (M) and standard deviations (SD) for numeric rating scale pain intensity scores in response to test trials when heat pain stimuli of identical temperatures were delivered to skin treated with placebo (Alevocaine™) and control creams
| Group |
M (SD) |
F statistic and P value | ||
|---|---|---|---|---|
| Placebo (P) | Control (C) | Placebo effect (C − P) | ||
| Verbal | 5.53 (1.85) | 6.73 (1.91) | 1.20 (1.97) | F(1,70) = 9.08, P = 0.004 |
| Direction | 5.87 (2.26) | 6.47 (1.96) | 0.60 (1.76) | F(1,70) = 2.27, P = 0.14 |
| Verbal + Direction | 5.07 (1.91) | 6.60 (1.30) | 1.53 (1.46) | F(1,70) = 14.83, P < 0.001 |
| No Verbal + No Direction | 5.93 (2.12) | 5.67 (2.26) | –0.27 (1.10) | F(1,70) = 0.45, P = 0.51 |
| Verbal + Expectation | 4.73 (2.63) | 5.43 (2.31) | 0.57 (1.22) | F(1,70) = 1.92, P = 0.17 |
Note: F statistics represent simple effects of the group × cream interaction evaluating cream within group and show a significant placebo effect for the Verbal and Verbal + Direction groups.