Scientific Method

Initial Observation• Use your senses to observe

-be objective (measure), not subjective (opinions)–See, hear, touch, taste, smell,

etc.• Can also use tools to

measure (label numbers)–Temperature, length,

volume, etc.

Which is the better observation?

• It is 58oF in the room.• It is cool in the room.

• The iguana likes lettuce.• The iguana consumed 90% of the lettuce.

• The bacteria is yucky.• The bacteria has a slimy appearance and smells of

sulfur.

State the Question

•“What is the effect of _____ on ____.”

Hypothesis

• “If…then…” If producing oxygen bubbles in photosynthesis is related to light color, then green light will increase photosynthesis oxygen bubbles to form.

• Dependent variable• Independent variable• prediction

Hypothesis

• 1. Must be testable – some way to check its validity

• 2. Must be falsifiable – must be some experiment that could show that it is not true (may not prove to be false, just have to be able to test that)

Can you test these to be falsifiable?

• 1. Animals are better than plants.• 2. The average tree height on the HS

campus is the same as on the MS campus.• 3. How many angels does it take to dance

on the head of a pin?• 4.

Writing a Hypothesis

• Common Hypothesis

• - educated guess

• - the general statement

• Formalized Hypothesis - Write the “If … and then…” format

• DO WORKSHEET TO PRACTICE WRITING IF…THEN HYPOTHESES

• DO WORKSHEET TO PRACTICE WRITING IF…THEN HYPOTHESES

A Controlled Experiment

• Only one tested variable at a time

• Manipulated Variable (Independent Variable) – one you change

• Responding Variable – (Dependent Variable)- one that changes as a result

Experiment

A. Independent Variable -what you change

goes on the X-axis of the graph

B. Dependent Variable -what changes as a result of what you did – goes on the Y-axis of the graph

Independent Variable?Dependent Variable?

Experiment• Constants-all the things in the

experiment that stay the samesame size Petri dishes

Same agar medium

Same type of bacteria

What constants are there in this experiment?

• Control – the part of the experiment that does not have the independent variable in it

• Use for reference, comparison• Often the normal condition

L-added oxygenM-control(no gas added)R-added carbon dioxide

What is the control set-up?

Do you think a placebo is a control?(inert pill, one without the drug)

• EX: some take Celebrex®, some take a sugar pill

Run the tests

Record the datagraphs charts

video write observations measurements

Celebrex – Placebo ExperimentResults

• Have we proven that Celebrex® (without a doubt) improves arthritis pain?

• What might be another explanation? Can we prove it false? 0

50

100

150

200

250

300

350

400

450

Celebrex

ImproveSame

Placebo

Conclusion

• Agree or disagree with the hypothesis

• The 10% spray produced taller plants.

Repeat the Experiments

Other scientists must be able to repeat your experiment with similar results to prove it true. OR they might prove it false.

NOW YOU WILL DESIGN AND RUN AN EXPERIMENT

• RECEIVE HANDOUT• CHOOSE GROUPS OF 4• DECIDE VARIABLE

-HAVE IT APPROVED• PLAN SET-UP• RUN 3 TRIALS• WRITE RESULTS