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.

Observations: Two Types

• Qualitative – describe what we observe– EX: The flower has white petals.– EX: Bob has blue eyes.

• Quantitative –measure what we observe– EX: The flower has seven petals.– EX: Bob has two eyes.

Try to make quantitative observations out of qualitative ones.• Qualitative: The dead fish is smelly.• Quantitative: You could ask a person to rate

the “smelliness” from 1-5.

TIPS FOR GOOD OBSERVATIONS

1. Be specific2. Use numbers3. Use terms others would understand4. Avoid using emotions, good/bad, or

opinions5. This is not the time for critical

evaluations…just state the facts.

Inference• Reasonable conclusions or a hypothesis

from observations you’ve made.• Use judgments based on past experiences or

and prior knowledge.

What inference can you make here?

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 the

independent variable on the dependent variable?”

• What is the independent variable here?What is the dependentvariable here?

Which are Better Problem Statements?

• What is the effect of temperature on the height of plants grown in soil?

• How tall do plants get?

• Why does that fish always swim to the top?• What is the effect of oxygen content on the

water on the swimming location of a fish in a tank?

1st do “Inferences or Observations” WORKSHEET

• 2ndGET A DOZEN CRICKETS WITH A CUP (hand on top)-Put them in the tank w/lid, please.

• 3rd Fill out “Cricket Observations and Inferences” and Problem Statement Worksheet

Observation

Inference

Problem Stat.

1234

PLAN CRICKET BEHAVIOR EXPERIMENT

• Laptops (2/lab table)

• Work on Cricket Fact Sheet

• Decide for your cricket behavior experiment:-problem statement

• -experiment set-up• (tomorrow will be a

test run)

(Enlarge to read captions)

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?

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 changegoes 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 dishesSame agar mediumSame 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

What is the control?

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

50100150200250300350400450

Celebrex

ImproveSame

Placebo

Conclusion

• Agree or disagree with the hypothesis

• The 10% spray produced taller plants.

Repeat the ExperimentsOther 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 CRICKET BEHAVIOR EXPERIMENT HANDOUT

• LAB GROUPS OF 4 (5)• BEHAVIOR VARIABLE• PLAN SET-UP• RUN 3 TRIALS• WRITE RESULTS

DUE DATES:

• Day 1 August 25-26 (Thurs. and Fri.)• Day 2 August 29 (Mon.)• Day 3 August 30 (Tues.)• Day 4 Aug. 31-Sept. 1 (BLOCK)• Day 5 Sept. 9 – (Fri.)

On Your Lab Table is the Behavior Variable

• A. Courtship or sexual• B. Agnostic behavior• C. Phototaxis• D. Territorial• E. Food-foraging• F. Stimulus kinesis.

HOMEWORK: Look up at least 5 web sites (see Sheldon Web Page) to research your Cricket Behavior Variable. (more is better)Print out at least 3.Write a summary page of ideas to design your experiment. (List or paragraph of at least 10 sentences.)