Designing an Experiment
The first part of designing your experiment is identifying what your dependent and independent variables are. Remember they are called variables because they can be changed. In a good experiment you will only change one variable at a time, so that you can identify if which variable is making the impact on the results. If your overall experiment is being performed in a selection of smaller experiments, then the variables may change in each smaller experiment. It is important to identify the variables for each experiment so that you can accurately discuss the outcome of the experiment.
Independent variables - This is the variable that is being set in the experiment. (In for Independent, In for Input). This variable will change due to the input from the dependent variable. The effect of this variable should be measured and recorded during the experiment. Dependent variables - This is the variable that is being changed during the experiment. (D for depenent, D for during). It will change by itself during the experiment as a result of the independent variable. The effect of this variable needs to be measured and recorded during the experiment. Controlled variables - These are variables that are not being tested but could affect the experiment. For example air pressure and temperature are common controlled variables in a high school experiment. You want to control these variables so that they remain consistent across the whole experiment. |
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Collecting Your Data
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Before you collect your data you need to determine what type of data you are going to collect in your experiment. There are three broad categories of data that can be collected:
- qualitative - quantitative - mixed methods There is no correct answer as to which type of data you should collect. In Physics we generally use quantitative data, as it is repeatable and generally independent of the observer, however which data type you should use depends on your particular question. Qualitative data is often described as descriptive data. It described what is observed in the experiment. For example the chemicals reacted to turn the mixture red. This data can be subjective as it can depend on who is observing the data. A good example of this is colour as different people perceive shades of colour differently. Some people may see a difference between shades of red in an experiment, where as others may not see a difference. Quantitative data is often described as empirical data. It describes the measurements that are taken during an experiment. For example length, speed or weight. This type of data is usually used in scientific studies as it is repeatable and not dependent on who is completing the study. It can be graphed or put into tables to make it easier to read. The average of the data can be collected to minimise errors in the data. It can also be used in calculations. However, by only collecting numerical data other effects of the variables may be missed. Mixed Method data is a technique where some quantitative and some qualitative data is collected. This can overcome some of the difficulties with each type of data. However, mixed methods can generate a lot of data. This can make the interpretation of the data difficult due to the amount of data that needs to be considered. It can hide any outcomes behind the noise of the data. It is usually more time consuming to analyse mixed method data. |