What is the typical alpha level used in psychology studies?

• A. 0.01
• B. 0.05
• C. 0.10
• D. 0.50

Answer: (B)

Alpha level is the cutoff you use to decide whether an observed effect is statistically significant. In psychology, the typical choice is 0.05, meaning you’re willing to accept a 5% chance of declaring an effect when there isn’t one (a false positive). This convention emerged historically and offers a practical balance between finding real effects and limiting false alarms given common study sizes and variability.

Choosing 0.05 isn’t a hard rule for all situations. A stricter level like 0.01 reduces false positives but also makes it harder to detect real effects (lower power). A more lenient level like 0.10 increases the chance of false positives but can be useful in exploratory research. When many tests are performed, researchers often adjust the threshold downward to keep the overall false positive rate under control. Thresholds as large as 0.50 aren’t used for significance because they would require very weak evidence to declare an effect.