let me quote from a readable text:
<<State the hypotheses. We begin by stating the value of a population mean
in a null hypothesis, which we presume is true. For the children watching TV
example, we state the null hypothesis that children in the United States watch an average of 3 hours of TV per week. This is a starting point so that we can decide whether this is likely to be true, similar to the presumption of innocence in a courtroom. When a defendant is on trial, the jury starts by assuming that the defendant is innocent. The basis of the decision is to determine whether this assumption is true. Likewise, in hypothesis testing, we start by assuming that the hypothesis or claim we are testing is true. This is stated in the null hypothesis. The
basis of the decision is to determine whether this assumption is likely to be true.
The
null hypothesis (H
0
)
, stated as the
null
, is a statement about a population
parameter, such as the population mean, that is assumed to be true.
The null hypothesis is a starting point. We will test whether the value
stated in the null hypothesis is likely to be true.
Keep in mind that the only reason we are testing the null hypothesis is because
we think it is wrong.
We state what we think is wrong about the null hypothesis in
an
alternative hypothesis.
For the children watching TV example, we may have
reason to believe that children watch more than (>) or less than (<) 3 hours of TV per week. When we are uncertain of the direction, we can state that the value in the null hypothesis is not equal to (≠) 3 hours. In a courtroom, since the defendant is assumed to be innocent (this is the null hypothesis so to speak), the burden is on a prosecutor to conduct a trial to show evidence that the defendant is not innocent. In a similar way, we assume the null hypothesis is true, placing the burden on the researcher to conduct a study to show evidence that the null hypothesis is unlikely to be true. Regardless, we always make a decision about the null hypothesis (that it is likely or unlikely to be true). The alternative hypothesis is needed for Step 2<<
read through the first six pages here:
http://www.sagepub.com/upm-data/40007_Chapter8.pdf
so we will be having a quiz about hypotheses testing and i cant still figure out the difference between the null hypothesis with alternative hypothesis. PLEASE HELP ME DIFFERENTIATE THE TWO. And i still get confused between one tailed test and two tailed test.. what's the technique to know if the problem is gonna be a one tailed test or two tailed test? please help me.. THANK YOU VERY MUCH.
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