The Scientific MethodPart Two: Unit One, Lesson 2.2By Margielene D. Judan

LESSON OUTLINE

Throwback: The Scientific Method Testing the Hypothesis Experimentation Three Types of Experiments Understanding Experimental Variables

THROWBACK: THE SCIENTIFIC METHOD

It is a systematic way of investigation in order to solve a problem.

THROWBACK: BASIC STEPS OF THE SCIENTIFIC METHOD

1. State the problem or ask questions. (Observation)

2. Form a hypothesis.

3. Test your hypothesis by experimentation.

4. Record and analyze data.

5. State a conclusion.

6. Report your findings.

The Scientific Method Flowchart

(always use this chart when making scientific investigations)

TESTING THE HYPOTHESIS

To test the hypothesis, the experiment should be a fair test (you change only one variable at a time while keeping other conditions the same).

To insure that your experiment is a fair test, you must change only one factor at a time while keeping all other conditions the same.

Control group- the part of the experiment without the variables being tested

Experimental group- the part that contains the variable being tested.

EXPERIMENTATIONBasically a test of hypothesis

When experimenting, you must also make predictions.

Predictions are forecasts of future events based on past observations.

THREE TYPES OF EXPERIMENT

1. Controlled experiment

2. Natural experiment

3. Field experiment

Controlled Experiments

an experiment or trial that uses controls, usually separating the subjects into one or more control groups and experimental groups.

A variable is a characteristic, number, or quantity that increases or decreases over time. It is anything that you can change or control in an experiment.

There are three kinds of variables: (next slide)

3 Kinds of Variables

Controlled variable- constant and unchanged in an experiment.

Independent variable- factors which you change or alter during the experiment

Dependent variable- response to an independent variable

Natural or Quasi-Experiments

No variable is being changed or altered Rely solely on observations to determine the

factors which caused the phenomenon

(ex. Astronomy. To prove that the earth is round, you don’t need to change any variables. You cannot change the amount of sunlight, nor the shape of the earth. You just need to determine or identify the factors which caused the phenomenon.)

Field Experiments

applies the scientific method to experimentally examine an intervention in the real world rather than in the laboratory

Often used in social sciences such as psychology, economics, and political science

Field- outside the lab/not conducted inside a laboratory

Example: (refer to your book p. 31)

A group of student tested the effect of fertilizer on the growth of plants. They used six plants that are 15 cm tall. They grouped the plants into two groups: A and B. They watered the plants in group A with 200 mL of plain water and in group B with 200 mL of fertilizer solution. They watered the plants twice a week with the same amount of water and exposed them to the same amount of sunlight. After three weeks, they measured the growth of the plants in each group.

Example: (refer to your book p. 31)

Treatment:

200 mL of plain water twice a week for 3 weeks

18 cm tall 32 cm tall

The following are the results:

Group A Group B

Treatment:

200 mL of fertilizer solution twice a week for 3 weeks

Question 1: Which is the experimental and control group?

Treatment:

200 mL of plain water twice a week for 3 weeks

18 cm tall 32 cm tall

Group A Group B

Treatment:

200 mL of fertilizer solution twice a week for 3 weeks

Answer: Group A- control groupGroup B-

experimental group

Treatment:

200 mL of plain water twice a week for 3 weeks

18 cm tall 32 cm tall

Group A Group B

Treatment:

200 mL of fertilizer solution twice a week for 3 weeks

Control group- the part of the experiment without the variables being tested(Group A has no variables tested. It is only watered with plain water. But a control group is important for us to be able to compare the results with the experimental group.)Experimental group- the part that contains the variable being tested. (Group B was watered with fertilizer [the variable being tested])

Question 2: Which is the controlled, independent, and dependent variables?

Treatment:

200 mL of plain water twice a week for 3 weeks

18 cm tall 32 cm tall

Group A Group B

Treatment:

200 mL of fertilizer solution twice a week for 3 weeks

Answers:

Controlled variableamount of sunlight, kind of plant, initial size of plantIndependent variable -amount of fertilizerDependent variable -growth of plant

Answer:Controlled variableamount of sunlight, kind of plant, initial size of plant

Controlled variable- constant and unchanged in an experiment.

Both groups are have the same amount of sunlight, kind of plant, and have the same size at start of the experiment.

Answer:Independent variable -amount of fertilizer

Independent variable- factors which you change or alter during the experiment

The difference between the experiment is that we used a fertilizer solution instead of water on group B.

Answer:Dependent variable -growth of plant

Dependent variable- response to an independent variable

As a result to the fertilizer (independent variable), there is a difference in their growth size.

Take note of these following terms. You need to be able to identify and differentiate each. They will always appear in our experiments and lab works.

Experimental and control group Controlled, independent, and dependent

variables A fair test

Laboratory Tomorrow/next meeting (by group): Bring the following

Three 250 ml transparent cups Cold, normal, and hot water Dropper Ink Two Stopwatches (1 is enough) Black, Blue, and Red Ballpen Ruler

Sources:

Science Links 7