Introduction to Scientific Method:

Observation and Data

Ms. Day/ Honors BiologyLecture #49/18/2014

• Observation: using your 5 senses to collect information

• Data: scientific information

• Inference: a logical conclusion or assumption based on your observations

DATA2 TYPES:

• Quantitative: includes observations or data that involves numbers (#’s), amounts or quantities

• Qualitative: includes observations that DO NOT involve numbers; Observations or data that is descriptive.

Scientific Method

What are the steps?**(Initial) Observation : use your 5 senses

1. State the problem or question: • What are you trying to solve or

research? 2. Form your hypothesis:

– an educated or logical prediction to answer your problem question; use your prior knowledge

– Not just a “guess”– IT MUST BE TESTABLE!!!– “If…then…because” statement

» Use independent, dependent variable & prior knowledge

3. Plan your experiment: • decide your procedure, control,

variables & materials

4. Perform your experiment: – Collect data (both qualitative and

quantitative) 5. Analyze your data (Results):

– Make sense of your data– put it in LINE graphs/charts/table, etc.

6. Conclusion: – Sum up your findings (data) – Restate your hypothesis and state whether

it is rejected or accepted based on your results

– CITE your quantitative and/or qualitative data!!! EXPLAIN your numerical data.

– State and EXPLAIN any experimental error(s) (called error analysis)

A Controlled Experiment

• Experiment = process to collect data

• There are (usually) 2 groups in an experiment:

1. Experimental (or test) group2. Control group

Experimental vs. Control Groups

Experimental (Test) Group

Control Group

• 1 variable (thing) changes or is tested

•Comparison group•No changes•“Normal” conditions

Example: HOW WILL FERTILIZER AFFECT PLANT GROWTH?

WITH FERTILIZER WITHOUT FERTILIZER

(plants normally don’t have fertilizer)

>>>>ONLY CHANGE (test) 1 VARIABLE (thing): THE PRESENCE OF FERTILZER

Conditions (or variables) that NEED to remainthe same for a controlled experiment:

• AMOUNT OF SUNLIGHT, • SOIL, • TYPE OF POT, • TEMPERATURE, • SPECIES OF PLANT

++TEST

GROUP CONTROL GROUP

• A controlled experiment will have different variables:

1.Constant variables2.Independent variable3.Dependent variable

Standard (constant) Variables

• Things that are kept EQUAL in all treatments (groups)

• Aka-control variables or constants• **NOTE: Different than

CONTROL GROUP

• A controlled experiment will have 2 different variables:

1. Independent variable (“If….then…)

2. Dependent variable (If…then…)

Independent Variable Dependent Variable

•The thing (variable) that you SET UP AS DIFFERENT at the beginning of the experiment.

•Ask “What variable changed in the experimental group?

•“WHAT ARE YOU TESTING or CHANGING?”

•The MEASURED outcome in the experiment.

•Ask “What is being measured/recorded?”

Independent Variable• What are you

testing/changing?• X-axis

Dependent Variable• What are you

counting/measuring? • Y-axis

0.5 1 1.5 2 2.5 30

0.51

1.52

2.53

3.5

Honors Biology Is Awesome

Independent variable goes here (units)

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X- Axis = Independent variable• If time is present, it is ALWAYS the x-axis

(independent variable)Y- Axis = Dependent variable

Example: HOW WILL FERTILIZER AFFECT PLANT GROWTH? WITH FERTILIZER WITHOUT FERTILIZER

(plants normally don’t have fertilizer)

Independent variable: WHAT ARE YOU TESTING?» Fertilizer

Dependent variable: WHAT ARE YOU MEASURING? » Plant Growth

++TEST

GROUP CONTROL GROUP

Now let’s practice with Spongebob…• Which people are in the control group? What is the independent

variable? Patty Power Mr. Krabbs wants to make Bikini Bottoms a nicer place to live. He has created a new sauce that he thinks will reduce the production of body gas associated with eating crabby patties from the Krusty Krab. He recruits 100 customers with a history of gas problems. He has 50 of them (Group A) eat crabby patties with the new sauce. The other 50 (Group B) eat crabby patties with sauce that looks just like new sauce but is really just the old sauce with food coloring. Both groups were told that they were getting the sauce that would reduce gas production. Two hours after eating the crabby patties, 30 customers in group A reported having fewer gas problems and 8 customers in group B reported having fewer gas problems.

• What is the control group? • What is the independent variable?• What is the dependent variable?

Group BType of Sauce

Amount of gas

Testing Hypotheses• Not just a “guess”• IT MUST BE TESTABLE!!!• “If…then…because” statement

– Use independent, dependent variable & prior knowledge

• Science can only test hypotheses that can be proven false• YOU CANNOT PROVE A HYPOTHESIS TO BE TRUE!!!

– SCIENCE = TESTABLE; BASED ON COLLECTED EVIDENCE CALLED DATA

– BELIEF = OFTEN BASED ON IDEAS OR OPINIONS NOT DATA

• New techniques and knowledge have made previously unscientific hypotheses available for testing

• Experiments either reject or fail to reject (often said to support) the hypothesis

• Rejection leads to modification or dismissal of hypothesis

Theory vs. Models• Scientists test hypotheses MANY times in

different ways! (i.e.- w/ new research tools, equipment, etc)

• Many “types” of knowing…science-based knowledge based on careful, repeated observations/testable hypotheses.

• THEORY = a well-tested explanation that is supported by A LOT of evidence (data) – Much broader than a hypothesis

• MODEL = physical, mental or mathematical representations of how people understand a process or idea

Additional Information…• Essential to ALL experiments is:

1)Replication!!!• You NEED to consider your number of trials

– Use the EXACT same conditions in EACH trial– Why?

• To determine if the results are consistent this INCREASES our confidence in the resulting data

• BUT…– A certain amount of variation is NORMAL!– Increasing trial # allows us to obtain an

AVERAGE RESULT from different trials.

Additional Information…• Essential to ALL experiments is:

2) Sample size– You NEED to consider your sample size

when drawing conclusions

– For example…– You are working with plants and decide to

plant 2 control plants and 2 test plants. – 1 test plant and 2 control plants die during

the experiment– WHAT HAPPENS NOW?

Additional Information…• Essential to ALL experiments is:

3) Clear procedure– Do NOT use pronouns!– Use “directional” language

• Example:– Place ______ in _____. – Fill 20 ml of water in a 50 ml graduated cylinder

– Someone MUST be able to REPEAT your procedure over and over to produce similar results!!

More practice with Spongebob…

• http://sciencespot.net/Media/scimethodconvar.pdf#search='spongebob%20variable%20worksheet’