IN two separate studies, the actual difference between
the means of a treated group and an untreated group is 3 points.
However, in one study, the σm1-m2 is very large and so the 3 points is
not found to be significant. In the other study, the σm1 - m2 is very
small and so the 3 points is found to be be significant. What might have
caused this big difference in the σm1-m2 for the two studies?
the variability of data to be true we accept the null hypothesis of 3 points and that is type I error or we accept the false expression of small or large values >/<3 as null hypothesis known type II error