When framing down the hypotheses for research is it required to write down both null and alternate hypothesis? or only null hypothesis is written and the alternate is rejected or accepted on the basis of the null hypothesis.
It is important to completely specify the study - which means that you should state both null and alternative hypothesis (there are different possible alternatives depending on your problem).
Further, clear statement of the alternative hypothesis is required especially if you are going to design your study on strict quantitative criterion. To be specific, the study design may involve determining how many observations should be collected to detect an effect of a specified size or sizes. This is addressed through the power function, which is the probability of rejecting the null hypothesis at a given effect size when the alternative hypothesis is true.
So to my opinion good study design requires specification of both hypotheses.
"it is always in the negation of null hypothesis"
This statement of the previous poster is not true. There are one-sided alternative hypotheses, two-sided alternatives, and even composite alternatives. Therefore, it is always import to specify the alternative hypothesis so that it is not misunderstood.
Writing both is recommended. Link attached.
http://statistics.about.com/od/Inferential-Statistics/a/The-Difference-Between-The-Null-Hypothesis-And-Alternative-Hypothesis.htm
http://www.uow.edu.au/student/qualities/statlit/module3/4.1usingnull/index.html
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