Null hypothesis: The statement being tested in a statistical test is called the null hypothesis H0.
Usually the null hypothesis is a statement of "no effect" or "no difference."
Alternative hypothesis: The claim about a population that we are trying to find evidence for is
the alternative hypothesis, written Ha. The alternative hypothesis is onesided if it states that a
parameter is larger than or smaller than the null hypothesis value. It is twosided if it states that
the parameter is different from the null value (it could be either smaller or larger).
We abbreviate the null hypothesis as H0 and the alternative hypothesis as Ha. Hypotheses always
refer to a population, not to a particular outcome. Be sure to state H0 and Ha in terms of
population parameters. Because Ha expresses the effect that we hope to find evidence for, it is
sometimes easier to begin by stating Ha and then set up H0 as the statement that the hopedfor
effect is not present.
The hypotheses should express the hopes or suspicions we have before we see the data. It is
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This note was uploaded on 02/27/2012 for the course STAT 121 taught by Professor Patticolling during the Winter '11 term at BYU.
 Winter '11
 PattiColling

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