1.1.3 Experimentation

Can you state about eight principles of experimentation? Learning objectives Can you state about eight principles of experimentation? Random Selection Replicaton Double-Blind Testing Sources of errors Planning & Design Safety Procedure Control Experiment Sample Size

What is an experiment? 1. An experiment is a controlled test. 2. Only one variable should be changed at a time. a. Independent variable – changed by the experimenter. (Hint: I change the Independent variable) b. Dependent variable (Responding) – the effect.

What is an experiment? 3. Constants do not change. 4. Controlled variables are those which could change, but are not allowed to. 5. Two parts to an experiment: a. Control group – normal conditions. b. Experimental group(s) – variables are changed. 6. Prediction is the goal of experiments.

How to organise an experiment OR The Principles of Experimentation Plan and design the experiment Be aware of Safety procedures Select organisms at random Use a large enough sample size Use a control group Use Double-blind testing Change one factor at a time Measure changes Analyze the results State possible sources of error Repeat the experiment

Learning check What is an experiment? It is a controlled test where only one variable is changed at a time.

An example of an experiment Observation: It has been suggested that large daily doses of Vitamin C protect against the common cold virus. Hypothesis: Vitamin C protects against the common cold virus

An example of an experiment Experiment design: Ten adult males in their mid twenties who are friends of the investigator were chosen to test the possible value of vitamin C. 5 of them were given 3000mg of vitamin C a day; the other 5 were given a placebo. Which is the control group? Which is the experimental group? Is this a good experiment?

Problems with experiment design All males All mid twenties All friends Not a large enough sample

A Good Experiment Should Have only one variable Use a large number of samples Use random selection Be repeated Use double blind testing

Learning objectives Random Selection Planning & Design Replicaton Can you state about eight principles of experimentation? Random Selection Replicaton Double-Blind Testing Sources of errors Planning & Design Safety Procedure Control Experiment Sample Size

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