Which of the following statements about null effects in stress research is TRUE?

• A. A null effect means the independent variable had a strong impact on the dependent variable.
• B. Null effects always indicate that the research hypothesis is correct.
• C. Null effects are never due to issues like low statistical power or measurement error.
• D. A null effect occurs when an experiment finds no statistically significant difference between groups.

Answer: (D)

Verified step by step guidance

1. Understand the concept of a null effect in psychological research: it occurs when the data show no statistically significant difference between groups or conditions, meaning the independent variable did not produce a measurable effect on the dependent variable.
2. Review each statement carefully and compare it to the definition of a null effect. For example, check if a null effect means a strong impact (which contradicts the definition).
3. Consider the implications of null effects in research, such as whether they always support the research hypothesis or if they can result from methodological issues like low statistical power or measurement error.
4. Recognize that a null effect does not confirm the research hypothesis; rather, it suggests that the data do not provide sufficient evidence to reject the null hypothesis.
5. Conclude that the true statement is the one that correctly defines a null effect as the absence of a statistically significant difference between groups, aligning with standard research interpretation.