Hello existential,
The null hypothesis in this case would be:
H0: ? = 35
where ? is the population mean. That is, you want to test whether the
population mean is 35, despite the fact that the sample mean is 25.
The alternative hypothesis depends on whether you want to perform a
one- or a two-tailed test. This depends on what you are interested in
checking. You could either be interested in knowing if the population
mean is different from 35 (either higher or lower than that value); or
you may only be interested in checking, for example, if the population
mean is lower than 35.
You can find a good explanation of this at the following link:
HyperStat -- One- and two-tailed tests
http://davidmlane.com/hyperstat/A65596.html
"A probability computed considering differences in both directions is
called a "two-tailed" probability. The name makes sense since both
tails of the sampling distribution are considered. There are
situations in which an experimenter is concerned only with differences
in one direction. [...] For instance, if a new drug treatment is
developed, the main issue is whether or not it is better than a
placebo. If the treatment is not better than a placebo, then it will
not be used. It does not really matter whether or not it is worse than
the placebo"
So, if you are performing a two-tailed test, the alternative hypothesis would be
Ha: µ ? 35
If you are performing a one-tailed test, the alternative hypothesis could be either
Ha: µ < 35
or
Ha: µ > 35
More information on the concept of null hypothesis can be found at
HyperStat -- Null Hypothesis
http://davidmlane.com/hyperstat/A29337.html
Google search terms
"null hypothesis"
://www.google.com.ar/search?hl=es&q=%22null+hypothesis%22&meta=
I hope this helps! If you have any questions regarding my answer,
please don't hesitate to request a clarification. Otherwise I await
your rating and final comments.
Best wishes!
elmarto |