Experimental Design

????????????????????????????What’s the question

HypothesisIf-then statementIf 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.

•To test only one variable

An experiment needs:

•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 C D

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 C D

What group is the control group?

• 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.

An experiment needs:

Data Collections

Beaker Test Tube PipetteGraduated Cylinder

Which is the most precise?

Accuracy - the ability of a measurement to match the actual quantity being measuredThe true value

Precision – the ability of a measurement to be consistently repeated

Meniscus

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.)