Level of Significance

 Level of Significance: 

    If the probability (P) of an event or outcome is high, we say it is not rare or not uncommon. But, if the P is low, we say it is rare or uncommon. In biostatistics, a rare event or outcome is called significant, whereas a non-rare event is called non-significant. The ‘P’ value at which we regard an event or outcomes as enough to be regarded as significant is called thesignificance level. In research, most commonly P value less than 0.05 or 5% is considered as significant level. However, on justifiable grounds, we may adopt a different standard like P < 0.01 or 1%. Whenever possible, it is better to give actual P values instead of P < 0.05. Even if we have found the true value or population value from sample, we cannot be confident as we are dealing with a part of population only; howsoever big the sample may be. We would be wrong in 5% cases only if we place the population value within 95% confidence limits. Significant or insignificant indicates whether a value is likely or unlikely to occur by chance. ‘P’ indicates probability of relative frequency of occurrence of the difference by chance.