The next step is to formulate an analysis plan, which outlines how the data will be evaluated. A potential null hypothesis implying a one-tail test is "this coin is not biased toward heads". If Alice conducts one of these tests, such as a test using the normal model, and proves that the difference between her returns and the buy-and-hold returns is significant, or the p-value is less than or equal to 0.
Now we've one problem: sample outcomes tend to differ somewhat from population outcomes. The null hypothesis claims that there is no difference between the two average returns, and Alice has to believe this until she proves otherwise.
Like so, some typical null hypotheses are: the correlation between frustration and aggression is zero correlation -analysis ; the average income for men is similar to that for women independent samples t-test ; Nationality is perfectly unrelated to music preference chi-square independence test ; the average population income was equal over through repeated measures ANOVA.
The explicit null hypothesis of Fisher's Lady tasting tea example was that the Lady had no such ability, which led to a symmetric probability distribution. There are clear exceptions to those alternate hypotheses, so if you test the wrong plants, you could reach the wrong conclusion.
Cohen, J Hence again, with the same significance threshold used for the one-tailed test 0. The traditional tests of 3 or more groups are two-tailed. We don't usually believe our null hypothesis or H0 to be true.