What does a P value of less than 0.05 indicate?

A P value of less than 0.05 indicates that there is a statistically significant result, meaning that the likelihood of the observed results occurring due to random chance is less than 5%. This threshold is often used in research to determine whether to reject the null hypothesis. A P value in this context suggests strong evidence against the null hypothesis, implying that the results are likely reflecting a true effect rather than random variation in the data.

In many scientific fields, a P value below 0.05 is considered an acceptable criterion for establishing significance, thus inferring with 95% confidence that the observed results are unlikely to have occurred under the null hypothesis, which posits no effect or difference. This does not imply certainty about the results' validity or the absence of other potential confounding factors; rather, it indicates a degree of reliability regarding the existence of an effect.

Understanding this concept is crucial because statistical significance does not automatically equate to practical significance, and further considerations regarding study design, effect size, and context should always be part of interpreting research findings.