Are Null Hypotheses Really True?
P is calculated under the assumption that the null hypothesis is true. Most null hypotheses tested, however, state that some parameter equals zero, or that some set of parameters are all equal. These hypotheses, called point null hypotheses, are almost invariably known to be false before any data are collected (Berkson 1938, Savage 1957, Johnson 1995). If such hypotheses are not rejected, it is usually because the sample size is too small (Nunnally 1960). To see if the null hypotheses being tested in The Journal of Wildlife Management can validly be considered to be true, I arbitrarily selected two issues: an issue from the 1996 volume, the other from 1998. I scanned the results section of each paper, looking for P-values. For each P-value I found, I looked back to see what hypothesis was being tested. I made a very biased selection of some conclusions reached by rejecting null hypotheses; these include: (1) the occurrence of sheep remains in coyote (Canis latrans) scats differed among
