What is the procedure called where participants are unaware of whether they are in the experimental or control groups?

The procedure where participants are unaware of whether they are in the experimental or control groups is known as the single-blind procedure. This method helps to eliminate bias that could arise from participants' expectations or perceptions about the treatment they are receiving. By keeping participants unaware of their group assignment, researchers can focus on obtaining objective data regarding the effects of the independent variable on the dependent variable, without the interference of participant beliefs or expectations.

In contrast, the double-blind procedure involves both the participants and the researchers being unaware of group assignments, which further reduces bias by preventing both sides from influencing the study's outcomes. A placebo-controlled trial specifically refers to research designs that involve an inert substance to compare against the actual treatment but does not specifically address the participants' awareness of their group status. Randomization techniques are methods used to assign participants to either experimental or control groups at random, but do not speak to their awareness of their group condition.