Experimental Design

Experimental Design

What is Good Experimental Design?

• ‌Experimental Design is a logical, consistent process

• It uses the SCIENTIFIC METHOD for stating, solving, and understanding problems in the natural world.

Why Perform Experiments?

• The goal of all experiments is to test ideas or hypotheses to solve or understand phenomena in nature

• This is all done to either create a new theory,

• or to add more evidence to support an existing theory

Multiple Choice

An experiment generally tests how one _________ is affected by another.

• Variable

• test

• scientist

• option

Multiple Choice

The more times that an experiment is repeated and the same results obtained, the more likely the results are _________.

• better

• observed

• valid

• used

Multiple Choice

A(n) ____________ is a special type of scientific investigation that is performed under controlled conditions.

• experiment

• lab

• inquiry

• hypothesis

What's the process?

• ‌OBSERVE Something

• Research or Infer to formulate a Hypothesis

• Design a Procedure to test that hypothesis

• Conduct an experiment and record data

• Analyze the Results

• Draw a Conclusion and communicate the results

Multiple Choice

Rene grew bacteria from the mouth on special plates in the laboratory.  She placed drops of different mouthwashes on bacteria on each plate.

• recognize a problem
• test the hypothesis with an experiment
• form a hypothesis   
• draw conclusions

Multiple Choice

Johathan’s data showed that household cockroaches moved away from raw cucumber slices.

• recognize a problem
• test the hypothesis with an experiment
• form a hypothesis
• draw conclusions

Multiple Choice

Susan said, “If I fertilize my geranium plants, then they will blossom faster.”

• recognize a problem

• test the hypothesis with an experiment

• form a hypothesis

• draw conclusions

Multiple Choice

Stephen predicted that seeds would start to grow faster if an electric current traveled through the soil in which they were planted.

• recognize a problem
• test the hypothesis with an experiment
• form a hypothesis
• draw conclusions  

Observations

• There are two types of observations:

• Qualitative Observations: These are made by ‌acquiring information using your senses or with special equipment.

• Quantitative Observations: ‌is acquiring and recording numerical data.

What's the Problem?

• ‌Careful observations lead to questions…

• A Problem Statement is a question that compares two variables.

• Example 1: What is the effect of the change in the length of daylight on the leaf color of deciduous trees?

• Example 2: Does the change in the length of daylight affect the leaf color of deciduous trees?

Multiple Choice

Jose saw bats catching insects after dark. He asked, “How do bats find insects in the dark?”

• ask a question

• test the hypothesis with an experiment

• form a hypothesis

• draw conclusions

Multiple Choice

Dana wants to know how different are synthetic fibers from natural fibers.

• recognize a problem

• test the hypothesis with an experiment

• form a hypothesis

• draw conclusions

What are variables?

• ‌A Variable is anything that changes.

• The variables compared in the problem statement are the INDEPENDENT & DEPENDENT variables.

• The IV is what is changed at the beginning of the experiment.

• The DV is what changes BECAUSE of the IV

• Example 1: What is the effect of the change in the length of daylight on the leaf color of deciduous trees?T

IV vs. DV

• ‌INDEPENDENT VARIABLE:

• ‌A variable YOU MANIPULATE or CHANGE at the BEGINNING of the experiment.

• The different variations of the IV are called the LEVELS of the IV.

• DEPENDENT VARIABLE:

• The Variable that changes as a result of the independent variable.

• The Variable that is measured and recorded.

Constants & Control

• IN ANY EXPERIMENT, YOU MUST CONTROL AS MUCH AS POSSIBLE.

• ‌Constants are variables that DO NOT CHANGE through the entire experiment. It is something that MUST REMAIN THE SAME!

• The Control is one of the levels of the IV.

• It is the group that is used TO COMPARE TO THE RESULTS FOR EACH LEVEL OF THE IV. 

Multiple Choice

A scientist is testing the impact of light and dark on the moth behavior by turning a light on and off. The DEPENDENT variable is...

• amount of light

• moth behavior/their reaction

• number of moths

Multiple Choice

Diego wants to know how drinking milk affects how tall Dora grows. Which is the independent variable?

• Drinking milk.

• Diego's growth.

• Dora's growth.

• Chocolate or plain milk.

Multiple Choice

What is the INDEPENDENT variable (cause)in this experiment?

"Which type of metal, copper or aluminum, conducts heat faster?"

• size of metal

• types of metal

• time it takes to heat up

• shape of the metal

Multiple Choice

What is the DEPENDENT variable (effect) in this experiment?

"Does eating breakfast improve test score?"

• eating breakfast or not

• the grade you got on the test

• what time you get up in the morning

• what you eat for breakfast

Multiple Choice

The variable the is changed on purpose is..

• Constant

• Control

• Independent Variable

• Dependent Variable

Multiple Choice

Experiment: How does watching TV during studying affect a student’s test grades?

The students grades are the ___________ variable.

• independent
• dependent

Multiple Choice

Experiment: Do roses grow more in height in partial or direct sunlight?
The growth height is the ____________  variable.

• independent
• dependent

Multiple Choice

Experiment: Does changing the wing shape to make it more narrow affect the distance a paper airplane will fly?

The wing shape is the ___________ variable.

• independent

• dependent

Multiple Choice

Experiment: How does the flavor of ice cream affect the speed of melting?

The flavor of ice cream is the ___________ variable.

• independent

• dependent