## Choosing a Hypothesis

 Getting Started General Instructions | Introduction to Your Study | Experimental Design | Stating a Hypothesis Descriptive Statistics Histograms | Central Tendency | Standard Deviation | Confidence Intervals Comparing Two Samples Samples and Populations | Choosing a T-Test | Independent T-Test | P-Values and T-Tables Important Concepts The Normal Distribution | Z Scores | Probability Distributions Levels You are currently on Stating a Hypothesis at level 1. Level 1 | Level 2 | Level 3 Next Topic Experimental Design | Frequency Histograms

### Explanation

What is a Hypothesis?
A lot of science involves developing theories and then conducting experiments to test whether predictions made by the theory are correct. If a theory makes enough predictions that are supported by experimental data, then the theory gains acceptance. A theory can describe something big (such as evolution, for example) or smaller (such as how coffee affects short-term memory). A single prediction made by a theory must be very specific, for example 'Drinking coffee improves short-term memory'.

These small, specific predictions are called hypotheses. You do not have to have a theory to think of a hypothesis. You could just wonder if an experiment would support a certain idea. For example, 'Horses run faster then zebras' would be a simple hypothesis.

A hypothesis is designed to be tested as being either supported or not supported by experimental data. This means that a hypothesis will have an opposite, which is the fact that the hypothesis should be rejected! There is a vocabulary that comes with all of this. Here it is:

• The experimental (or research) hypothesis is the prediction that your theory makes, or the effect you suspect you will see. This is referred to as H1.
• The null hypothesis is the statement that the effect described in the experimental hypothesis does not exist. This is referred to as H0.
One thing to remember when wording your hypotheses is that it is important to decide whether or not you expect to see a difference in a particular direction. If you think that coffee improves memory, then you expect memory scores to be better for coffee drinkers, so there is an expected direction. You will see later that this expected direction is important, so think carefully about direction when you phrase your hypothesis.

### Exploration

Here are a list of sentences that represent either an experimental hypothesis or a null hypothesis. Some of them do not represent a hypothesis at all. Work through them saying which category each falls into and say whether the hypothesis has a direction or not.
Alchohol consumption does not effect reaction time
Does the above hypothesis have a direction?
The theory of evolution
Does the above hypothesis have a direction?
Sports drinks improve recovery time after exercise
Does the above hypothesis have a direction?
There is intelligent life out in space
Does the above hypothesis have a direction?
There is a difference between the ability of girls and boys to learn statistics
Does the above hypothesis have a direction?

### Application

Here are the two hypotheses from your study. Which is the null and which is the experimental hypothesis?
Sms treatment will increase motivation
Sms treatment will not increase motivation
Is your experimental hypothesis looking for an effect in a certain direction?
 Experimental Design | Frequency Histograms