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# Three types of hypotheses * Simple hypothesis

* Complex hypothesis

* Null hypothesis

### What is a hypothesis

A hypothesis states your predictions about what your research will find. It is a tentative answer to your research question that has not yet been tested. For some research projects, you might have to write several hypotheses that address different aspects of your research question.

A hypothesis is not just a guess — it should be based on existing theories and knowledge. It also has to be testable, which means you can support or refute it through scientific research methods (such as experiments, observations and statistical analysis of data).

### Variables in hypotheses

Hypotheses propose a relationship between two or more variables. An independent variable is something the researcher changes or controls. A dependent variable is something the researcher observes and measures.

Daily apple consumption leads to fewer doctor’s visits.

In this example, the independent variable is apple consumption — the assumed cause. The dependent variable is the frequency of doctor’s visits — the assumed effect.

## Three steps to hypothesis testing

• State the null hypothesis and alternative hypothesis
• Decide on test static and critical value
• Compute p-value. If P-value is less than the critical value reject the null hypothesis and accept the alternative hypothesis

### Simple hypothesis

Simple hypotheses are ones which give probabilities to potential observations. The contrast here is with complex hypotheses, also known as models, which are sets of simple hypotheses such that knowing that some member of the set is true (but not which) is insufficient to specify probabilities of data points.

### Complex hypothesis

Complex hypothesis is that one in which there are multiple dependent as well as independent variables. Example: Global warming causes icebergs to melt which in turn causes major changes in weather patterns.