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.
Statistical significance is typically defined when the chance of falsely rejecting the null hypothesis is less than 0.05. To put it another way statistical significance occurs when there is less than a 5% chance that the measured result between groups is truly present and not just due to random effects. Practical significance as the name implies denotes the real world importance of any statistically significant result. In health research, this is referred to a the minimal clinical important difference (MCID).