APA Dictionary of Psychology

in statistical significance testing, the likelihood that the observed result would have been obtained if the null hypothesis of no real effect were true. Small p values (conventionally, those less than .05 or .01) suggest that the chance of experimental results mistakenly being attributed to the independent variables present in the study (rather than to the random factors actually responsible) is small. Traditionally, the null hypothesis is rejected if the value of p is no larger than the significance level set for the test. Also called probability value.