# Experimental Design - PowerPoint PPT Presentation

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Experimental Design. ????????????????????????????. What’s the question. Hypothesis. If-then statement If part - shows a relationship (can be cause-effect) Then part – is your prediction

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Experimental Design

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### ????????????????????????????

• What’s the question

### Hypothesis

• If-then statement

• If part - shows a relationship (can be cause-effect)

• Then part – is your prediction

• If the texture/pattern of a paper towel affects the rate at which it picks up water, then a paper towel with more indentations and therefore surface area will pick up water the fastest.

An experiment needs:

• To test only one variable

• All other variables are constant

• Example: To test which fertilizer is the most effective, the variable is the type of fertilizer.

• What should you keep constant?

### An experiment needs:

• Control Group – Where all factors are standard or kept the same. This is what you will compare your experimental group to

• Experimental (Variable) Group – All conditions are kept constant EXCEPT for the variable

### Experiment

A

B

D

C

What group is the control group?

### An experiment needs:

• Independent (Manipulated) Variable – The factor that you deliberately change (fertilizer)

• Dependent (Responding) Variable – The factor that changes in response to the manipulated variable (plant growth)

### Experiment

A

B

D

C

What group is the control group?

An experiment needs:

• Data- the more trials or the larger the sample size, the more reliable your data will be.

• Quantitative- numerical data

• Qualitative- descriptive data

• Your data will need to be organized so that the result is clear.

• ### Data Collections

BeakerTest TubePipette

Which is the most precise?

• Accuracy - the ability of a measurement to match the actual quantity being measured

• The true value

• Precision – the ability of a measurement to be consistently repeated

### An experiment needs…

• Conclusions- your experimental results need to be communicated to

• Hypothesis- the prediction and the thinking behind your prediction

• For example: Fertilizer A will be the most effective in aiding plant growth because it contains the most nutrients.

• Theory- after many hypotheses have been tested and have not been proven incorrect, the hypotheses will become a part of a theory.

• Theory-

• How have you heard this word used in “the real world”?

• Why is it important that we know the scientific definition?

• Law- a mathematical explanation of a repeated occurrence (gravity, etc.)