Effect size is important, because all events in the real world except for true random numbers have some correlation. Eating an apple might help a broken leg he

Effect size is important, because all events in the real world except for true random numbers have some correlation. Eating an apple might help a broken leg heal faster or slower. There is certainly an extremely small correlation, and with a sufficiently large number of controlled experiments, a result rejecting the null hypothesis with p < 0.05 will be found. The required number of experiments might be astronomically large, but if any correlation exists, it can be found with enough samples. But without looking at the effect size, the result is useless. Even if eating an apple helps your broken leg heal 2 seconds faster on average, it is pointless to suggest this as medical advice.