The null hypothesis is the contention that an effect being studied does not exist. This is the default hypothesis that the difference between two conditions can be quantified as zero. If a significant effect is found, it is said that the null hypothesis can be rejected. You can think of it as a kind of scientific "presumption of innocence." Until we actually check, we don't REALLY know. Even then, we can't ever really say that the null hypothesis has been proved or disproved in an ultimate sense. Even after we check, we don't really KNOW. Truth about the world will always be asymptotic in that way. Probably.

edie b is following