The Scientific Method

Unit 1: The Scientific Method

Chapter 1-1 & 1-2

Scientific Method

The scientific method is a problem-solving procedure used by scientists to seek answers to questions.

Scientific Method1. Identify a Problem2. Create a Hypothesis3. Design and perform an

experiment.4. Record Data and Analyze5. State a Conclusion 6. Check for sources of error

1. Identify a ProblemObservations are

descriptions about the way something is or the way things happen

From these observations, a question is formed about why or how

Checking for understanding

Barney observes: – When I drink Coke, I burp a lot.

What is a question that Barney can ask Professor Frink?

A Hypothesis is a prediction that can be tested– Should be written in the form of

an “If…, then…” statement

2. Create a Hypothesis

Checking for understanding

If people ______________, then they will ______ more.

Can this hypothesis tested?

Hypothesis vs. Theory Hypothesis: a prediction that can be

tested and may or may not be true Theory: a well-tested explanation

that is supported by many types of evidence.– In science, theories are nearly facts– Ex. Theory of Evolution, Theory of Relativity,

Cell Theory

3. Controlled ExperimentHypothesis is testedProcedure—the steps

followed during an experiment

Controlled experiments have experimental group(s) & a control group

Example: Professor Frink wants to

determine if Coke will increase the frequency of burping.

He gives 10 volunteers (subjects) from Springfield Coke and another 10 subjects water. All other conditions are kept the same.

•All people are 20-30 years old•All people are healthy.•All people have to not eat or drink

for 3 hours before the experiment.

Subject

Variable: anything that can influence the outcome of the experiment

Control Group: group where all variables are kept the same– Used as “normal” for comparison

Experimental Group: group(s) where all the variables are the same except the one variable being tested

Checking for understanding

Professor Frink gives 10 volunteers (subjects) from Springfield Coke and another 10 subjects water.

•All people are 20-30 years old•All people are healthy.•All people have to not eat or drink for 3

hours before the experiment Which group is the control group? Which group is the experimental group? What are the variables that are being

controlled?

Independent Variable: What is being tested– The variable that is changedThe variable that is changed

Dependent Variable: What is measured or observed– The variable that changes because

of the independent variable

Checking for understanding

If people drink Coke, then they will burp more.

Professor Frink gives 10 volunteers (subjects) from Springfield Coke and another 10 subjects water.

What is the independent variable? What is the dependent variable?

If people drink Coke (independent variable),

then they will burp more (dependent variable).

4. Record Data & Analyze Collect & record Data

(information)•Data can be recorded in a table

Analyze the data by graphing it– Bar graphs: show comparisons– Line graphs: show changes over

time

Example:Average # of Burps

Control Group: Water

2

Experimental Group:

Coke

6

Independent Variable

Control

Dependent Variable: what you measure

Example:

Y-a

xis

= D

ep

en

den

t V

ari

ab

le

X-axis = Independent Variable

Title

Label

Occurrence of Gas Expulsion for Non-carbonated vs. Carbonated Beverages

0

1

2

3

4

5

6

7

WATER COKE

# OF BURPS

Average Number of Burps for Water vs. Coke

Proper units

Type of Beverage

5. Conclusions

If the results are in agreement If the results are in agreement with the hypothesis then the with the hypothesis then the hypothesis is hypothesis is ““acceptedaccepted”.”.

If the results disagree with the If the results disagree with the hypothesis then the hypothesis hypothesis then the hypothesis is is ““rejectedrejected””

Checking for understanding In the example is the In the example is the

hypothesis accepted or hypothesis accepted or rejected? rejected? – ACCEPTED!ACCEPTED!

Why? Why? – There were more burps There were more burps

with Coke than with with Coke than with water based on the data water based on the data and the results of the and the results of the graph.graph.

Sources of error: things that may effect the results of the experiment

*Error can make the results of an

experiment not valid!!! – Always look at the set-up of an

experiment to check for error.

6. Check for sources of error

Possible sources of error:

– Small sample size: fewer subjects may give inaccurate results

– Unequal group size: you can’t compare the results of 2 groups if one group has 10 subjects and the other group has 50 subjects

Possible sources of error: (cont)

– Not controlling (keeping the same) all variables except the one being tested• Length of the experiment (hours vs. days)• Amount of the variable (2 cokes vs. 1)• Type of material (coke vs. pepsi)• Other: light, temperature, age, health,

gender, etc

Repeat the work:– When a hypothesis is supported

by data from additional investigations, it is considered valid.

When a hypothesis is not supported, it means that we need to go back and ask new questions.

Checking for understanding

Two students decide to test the effects of Miracle-Gro fertilizer on plant growth. – They buy a rose plant and a daisy plant. – The roses are given Miracle-Gro and 1 cup of

water/day and the daisies are given ½ cup of water/day.

– The roses are kept in the sun and the daisies are kept in the shade.

– The growth of the roses is measured daily and the daisies are measured each week.

What are some sources of error in this experiment?