Scientific Method

Systematic Approach

• Six Steps• State the problem/question• Gather information on the problem• Form a hypothesis

• If…then…because…

• Perform experiments• Record and analyze data• State Conclusion

State the Problem/Questions

• Develop a clear statement defining the problem

• Make sure your problem is narrowed/specific enough

Gather Information

• Write down all information you already know

• Do research in books on the topic you are investigating

• Ask experts on the subject you are researching

• If you find an answer to your problem/question you do not need to move on

Suggest a possible solution to your question

May be right or wrong Should be based on the research Should be in the correct format:

› If (independent variable), then (dependent

variable, because (what you will change)

Perform Experiments

• Develop a test to prove or disprove your hypothesis• Must be run multiple times• Must have only 1 independent

variable (the factor being tested• Must include 2 setups

•Experimental setup•Control setup

Experimental Setup

• Part of the experiment containing the independent variable• Independent variable – part of the experiment you

are changing

• Must have only 1 independent variable to ensure the results are accurate

• Example:• Plant with dirt, water, sunlight, 25oC and fertilizer

(this is the independent variable if you are testing the effects of fertilizer)

Control Setup

• Setup exactly the same as the experimental setup, except it does not include the variable

• Example:• Plant with same amount of dirt, same

kind of dirt, same water, same temperature, and same sunlight, DOES NOT have any fertilizer

Variables

• Independent Variable• 1 thing you are testing• 1 thing you change between experiments

• i.e. amount of fertilizer, brand of fertilizer or amount of water

• Dependent Variable• Thing that changes because of the independent

variable• You do not control• i.e. Number of leaves on the plant, height the plant

grows, amount of fruit it produces

Record and Analyze Data

• Recording Data• Any observations and measurements• Must write every observation down• Must be consistent in when you are checking your

experiments and recording the results• Can be recorded as tables or charts

• Analyzing Data• Must be looked at to determine patterns• Can make into graphs• Must Complete all necessary mathematical

calculations• Answer any questions from the lab

Observations

• Qualitative Observations• Observations describing the

experiment• i.e. Color, smell, touch, taste, look

• Quantitative Observations• Observations with numerical values

and units• i.e. Height in cm, length in m, number of

leaves

State a Conclusion

• Paragraph (minimum of 5 sentences)• Decide if you hypothesis is correct or

incorrect• State what proved or disproved your

hypothesis• Use data in your description• State errors you may have made• State future tests to be run

A hypothesis is a tentative statement that proposes a possible explanation to some phenomenon or event.

A useful hypothesis is a testable statement which may include a prediction.

The key word is testable. That is, you will perform a test of how two variables might be related. This is when you are doing a real experiment. You are testing variables.

Any laboratory procedure you follow without a hypothesis is really not an experiment. It is just an exercise or demonstration of what is already known.

How Are Hypotheses Written?

1.Chocolate may cause pimples. 2.Salt in soil may affect plant growth. 3.Plant growth may be affected by the color of the light. 4.Bacterial growth may be affected by temperature.

All of these are not examples of hypotheses because they use the tentative word "may“. Using the word may does not suggest how you would go about proving it.

If we say "Trees will change color when it gets cold“ we are making a prediction. Or if we write, "Ultraviolet light causes skin cancer" could be a conclusion.

One way to prevent making such easy mistakes is to formalize the form of the hypothesis.

Formalized Hypotheses example:

If skin cancer is related to ultraviolet light , then people with a high exposure to UV light will have a higher frequency of skin cancer.

If leaf color change is related to temperature , then exposing plants to low temperatures will result in changes in leaf color.

Notice that these statements contain the words, if and then.

If you always ask yourself that if one thing is related to another, then you should be able to test it.

Formalized hypotheses contain variables.

3 TYPES OF VARIABLES1. Independent (Manipulated) Variable2. Dependent (Responding) Variable3. Controlled Variable

The independent variable is the one you, the "scientist" control and the dependent variable is the one that you observe and/or measure the results.

INDEPENDENT (MANIPULATED) VARIABLE

• The variable that can be changedduring an experiment• The variable that may cause achange in the dependent variable

DEPENDENT (RESPONDING) VARIABLE

•The factor that is being measuredin an experiment•The variable that may changebecause of the independent variable

CONTROL VARIABLE(CONSTANT)

•Variable that stays the same duringan experiment•Variable that is controlled by thescientist•Variable that is not allowed tochange

Daily Assignment: Rewrite the first four hypotheses using the formalized style. Single underline the dependent variable and double underline the independent variable in the If clause of each hypothesis. When you are done, write one more original hypothesis of your own using this form.

Independent Variable- RedDependent Variable – BlueControl- Green

1. Chocolate my cause pimples. 2. Salt in soil may affect plant growth. 3. Plant growth may be affected by the color of the light. 4. Bacterial growth may be affected by temperature.

1. If 5 ounces of chocolate is eaten for three straight days, then pimples will appear.

2. If

1. If 5 ounces of chocolate is eaten three days in a row, then pimples will appear.

2. If 2 cups of salt is added to the soil, then the plant will not grow.

Independent Variable- RedDependent Variable – BlueControl- Green1. Chocolate my cause pimples. 2. Salt in soil may affect plant growth. 3. Plant growth may be affected by the color of the light. 4. Bacterial growth may be affected by temperature.