Let's further define mutation as a heritable change in the genetic material. This point becomes important in multicellular organisms where we must distinguish between changes in gametes (germline mutations) and changes in body cells (somatic mutations).
Statistical significance relates to the question of whether or not the results of a statistical test meets an accepted criterion level. In psychology this level is typically the value of p < .05. The criteria of p < .05 was chosen to minimize the possibility of a Type I error, finding a significant difference when one does not exist. It does not protect us from Type II error, failure to find a difference when the difference does exist.
If the p value falls below a conventionally accepted threshold (say .05), we might judge the result to be statistically significant. The substantive significance of a result, in contrast, has nothing to do with the p value and everything to do with the estimated effect size. Only when we know whether weâre dealing with a large or trivial sized effect, will we be able to interpret its meaning and so speak to the substantive significance of our results.