Question

which of the following is not a \control\ in an experimental procedure? a placebo a known standard of comparison a normal group an experimental group a \zero\-value group

Explanation:

Controls in experiments are groups or standards used to provide a baseline for comparison, ensuring the experimental variable's effect is measured accurately. A placebo, known standard, normal group, and zero-value group all serve as control baselines. The experimental group is the one exposed to the test variable, not a control.

Answer:

an experimental group