Which control technique controls for both known and unknown variables?

Which control technique controls for both known and unknown variables?

(a) Building the extraneous variable into the design

(b) Matching

(c) Random assignment

(d) Analysis of covariance

✅ Correct option: (c) Random assignment

Explanation:

Random assignment is the most powerful control technique available to researchers because it controls for both known and unknown extraneous variables. By randomly assigning participants to experimental and control groups, researchers ensure that individual differences are distributed evenly across groups. As a result, no systematic bias favors one group over another. Unlike matching, which only controls for known variables such as age or intelligence, random assignment neutralizes the effects of variables that the researcher may not even be aware of. This is why random assignment is considered the cornerstone of true experimental design. Building extraneous variables into the design and using analysis of covariance (ANCOVA) require prior identification and measurement of confounding variables, limiting their scope. Random assignment eliminates this limitation and strengthens internal validity by supporting causal conclusions.

10 Related PPSC Facts:

Random assignment differs from random sampling. It improves internal validity. It controls individual differences. It equalizes unknown variables. True experiments require random assignment. Matching controls only known variables. ANCOVA is a statistical control. Randomization reduces selection bias. Coin toss is a simple random method. Lack of random assignment leads to quasi-experiments.