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Null hypothesis statistical significance testing

What is a Hypothesis Statement?

If you are going to propose a hypothesis, it’s customary to write a statement. Your statement will look like this:
“If I…(do this to an independent variable)….then (this will happen to the dependent variable).”
For example:

  • If I (decrease the amount of water given to herbs) then (the herbs will increase in size).
  • If I (give patients counseling in addition to medication) then (their overall depression scale will decrease).
  • If I (give exams at noon instead of 7) then (student test scores will improve).
  • If I (look in this certain location) then (I am more likely to find new species).

A good hypothesis statement should:

  • Include an “if” and “then” statement (according to the University of California).
  • Include both the independent and dependent variables.
  • Be testable by experiment, survey or other scientifically sound technique.
  • Be based on information in prior research (either yours or someone else’s).
  • Have design criteria (for engineering or programming projects).

What is Hypothesis Testing?

hypothesis testing

Hypothesis testing in statistics is a way for you to test the results of a survey or experiment to see if you have meaningful results. You’re basically testing whether your results are valid by figuring out the odds that your results have happened by chance. If your results may have happened by chance, the experiment won’t be repeatable and so has little use.

Hypothesis testing can be one of the most confusing aspects for students, mostly because before you can even perform a test, you have to know what your null hypothesis is. Often, those tricky word problems that you are faced with can be difficult to decipher. But it’s easier than you think; all you need to do is:

  1. Figure out your null hypothesis,
  2. State your null hypothesis,
  3. Choose what kind of test you need to perform,
  4. Either support or reject the null hypothesis.

What is the Null Hypothesis?

If you trace back the history of science, the null hypothesis is always the accepted fact. Simple examples of null hypotheses that are generally accepted as being true are:

  1. DNA is shaped like a double helix.
  2. There are 8 planets in the solar system (excluding Pluto).
  3. Taking Vioxx can increase your risk of heart problems (a drug now taken off the market).