Designing an experiment
If someone says that they are going to experiment on you, right away you know that they are going to use you as a guinea pig. They are going to do something to you. You are part of the experimental group. However, in order for them to know if what they are doing to you really works, they need to compare you to someone whom they did not experiment on. This person would be the control group.
An experiment always consists of an experimental group and a control group.
The experimental group is the group receiving the treatment, or the group that something is being done to.
The control group does not receive the treatment. The control group is the standard for comparison. The control group is not experimented on.
When you are asked to design an experiment, you should write down the questions that you are trying to answer. That is the problem.
Your hypothesis is what you believe is going to happen and this statement should be generated based on some previous experience or research on this topic. The hypothesis should be carefully written to answer the questions and also formatted in a way, which can be tested. This can be done by saying what you are going to do and what you expect to happen as a result of what you do. For example, what is the effect of increasing physical activities on pulse rate? HYPOTHESIS: If you increase your physical activities, then your pulse rate will increase.
NOTE: A well written hypothesis always consist of an independent and a dependent variable.
The dependent variable is what is being observed or measured. In this case, the dependent variable is the pulse rate.
The independent variable is the treatment or the only factor in an experiment that can be manipulated or changed. In this case, the independent variable is increasing physical activities.
ANOTHER WAY OF LOOKING AT THINGS is cause and effect. The independent variable is the cause and the dependent variable is the effect.
NOTE The dependent variable depends on the independent variable. The independent variable you know before the experiment and the dependent variable you find out after the experiment.
OBSERVATION: Probably is the most important step in the scientific method. We observe using our five senses. (Sight, taste, smell, touch and hear).
The experiment is a test of the hypothesis.
Data is information that is collected during the experiment.
We analyze data after the experiment by looking for patterns using graphs, tables and charts,
Conclusion is an explanation of the data. (after the experiment)
Inference: A conclusion based on observation or evidence.
Theory is a hypothesis that is supported by many experiments or a broad explanation of natural events that is supported by strong evidence of repeated experiments.
The characteristics of a good experiment
- In an experiment, the sample size should large (test many subjects) to make up for genetic differences of other inconsistencies.
- Can be repeated by anyone and get the same results.
- Test only one variable.
- Does not have to agree with the hypothesis.
Sample Problem
An experiment was carried out using ten plants of the same species. Growth hormones were added to the soil for the purpose of making the plants grow taller.
State the hypothesis.
- If you add growth hormones to plant soil, then the plants will grow taller.
- The control group will not receive any hormones and the experimental group will.
- The growth hormones
- Plant height
- Same amount of water and same amount of sun
- Use more plants
- Repeat the experiment
- Use different species of plants
- If the plants in the experimental group grow taller than the control group, my hypothesis is supported.
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