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Figure 4 | Trials

Figure 4

From: Interaction between drug and placebo effects: a cross-over balanced placebo design trial

Figure 4

Placebo effect on caffeine plasma levels and systolic blood pressure. A & B: Mean plasma caffeine levels over 14 hours after administration of caffeine to 22 participants in a balanced cross-over design before (A) and after natural logarithmic transformation (B). C: Systolic blood pressure over four hours following intervention. Squares indicate receiving 300 mg caffeine described as caffeine (open square with continuous line) or as placebo (closed square with interrupted line). Triangles indicate the administration of placebo described as placebo (open triangle with continuous line) or as caffeine (closed triangle with interrupted line). T bars indicate standard errors.

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