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← Theoretical 2

Q82 — Experimental Design Limits — Herbal Treatment and Statin Co-Therapy

Theoretical 2 Real exam question — full text reproduced under IBO's CC BY-NC-SA 4.0 license
Cardiovascular Physiology

A herbal treatment was tested on patients with lipid imbalance in their blood. Patients with lipid imbalance in the blood were divided into two groups — the control group received a placebo, while the intervention group received a herbal preparation. During the experiment, which lasted 6 weeks, both patient groups received statin therapy, which inhibits cholesterol production in the liver. At the end of 6 weeks, both groups were measured for average cholesterol, high-density lipoprotein (HDL) and low-density lipoprotein (LDL) levels in the blood, and the results were plotted in a bar chart to compare against pre-treatment levels.

Bar chart of total cholesterol before and after treatment, comparing the intervention and placebo groups; after treatment the intervention group shows a significantly larger decrease (marked **). Cholesterol levels before and after the 6-week trial, intervention vs. placebo.

Bar chart of HDL before and after treatment, comparing the intervention and placebo groups; after treatment the intervention group shows a modest, significant increase (marked *). HDL levels before and after the 6-week trial, intervention vs. placebo.

Bar chart of LDL before and after treatment, comparing the intervention and placebo groups; before treatment the two groups are similar, but after treatment the intervention group shows a significantly larger decrease (marked **). Figure 1. Summary of the results of a controlled experimental trial of the herbal preparation intervention. * and ** indicate statistically significant differences compared to placebo.

Using the information and the data in the graphs, determine which of the statements are true or which are false.

A. The results in this figure alone are sufficient to assert that statin therapy decreases cholesterol levels in the blood.
B. The information presented here is not sufficient to claim that herbal preparation would reduce LDL levels in the absence of a statin therapy.
C. The reduced LDL concentration in the intervention group relative to the control group could imply an improved cardiovascular prognosis for patients in the intervention group.
D. The LDL-reducing effect of the herbal preparation after 6 weeks cannot be established since the case group had a lower LDL concentration to start with.
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Question reproduced from IBO 2022, Theoretical Paper 2, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)