The Scientific Method

Scientific method• the process scientists use to investigate a

problem, question, and/or observation

Steps in the Scientific Method

I. Making Observations and Asking Questions (leads to a problem to investigate)

II. Developing a Hypothesis

III. Doing the Experiment (includes identifying variables, constants, and control group and writing a procedure)

IV. Collecting and Analyzing Data

V. Forming a Conclusion

VI. Communication

The Scientific Method: Making Observations– An observation is when you

use your senses to obtain information.

– There are 2 types of observations:

• Quantitative: involve numbers and measurements

• Qualitative: use your 5 senses

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The Scientific Method: Making Observations

Observations vs. Inferences

Inference: a logical explanation for an observation; not a fact

Can only be used in the conclusion of a lab

1.3

Observations

• That plant is extremely wilted.

• The car stopped running

• The Sox are leading their division

Inferences

• That plant is extremely wilted due to a lack of water.

• The car stopped running because it was out of gas.

• The Sox are leading their division because they are playing well right now.

The Scientific Method: Developing a Hypothesis

• Hypothesis

– a prediction for a question; a proposed

explanation for an observation

– written as an “if…then…” statement

• Example: If I put more weight on the pirate ship

ride, then it will slow down because the extra

weight will cause it to not flow as freely.

1.3

The Scientific Method: Doing the Experiment

• Experiment

– a procedure that is used to test a hypothesis

• Variables

– Factors that change in an experiment

• Groups

– The people or things tested in an experiment

• Procedure

– A detailed, step-by-step description of how you will conduct your experiment; includes the materials needed

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Variables

• Independent variable:– The factor that the experimenter changes during the

experiment; if you are the experimenter you say it’s the variable “I” change; follows ‘if’ in a hypothesis• Example: If I change the weight in the pirate ship ride…

• Dependent variable:– The factor that changes in response to the independent

variable; experimenter makes observations of this variable; follows ‘then’ in a hypothesis• Example: …, then the number of swings will reduce.

• Constants

– Factors that stay the same throughout the entire experiment• Example: length of pendulum’s swing, height at which

pendulum is dropped, person who drops pendulum

Groups• Control group

– The group of people or things that is NOT influenced by the independent variable, and is used to compare to the experimental group

• Example: A pirate ship that has NO weight in it.

• Experimental group

– The group of people or things that is influenced by the independent variable, and is compared to the control group

• Example: The pirate ships with weight in them.

1.3

Testing

• Experiments require many trials to improve accuracy

• Trials

– Repetitions of testing during the experiment

Scientific Method: Collect & Analyze Data

• Data: recorded observations made during an experiment; can be qualitative and quantitative

• Data table: a visual display of data using rows and columns; typically organized by trials (repetitions during the experiment)

Draw a Data Table

Micah asked all of his classmates what their favorite animals are. He found that 12 students liked dogs, 5 students liked cats, 3 students like horses, and 1 student liked bearded dragons.

Scientific Method: Collect & Analyze Data

• Graph:

– a visual display of quantitative data

– there are four major parts to a graph:

Title

Axis Scales Independent

Variable

Dependent

Variable

Draw a Graph Favorite Animals of Ms. Henry’s Class

Animal Number of Students

Dog 12

Cats 5

Horses 3

Bearded Dragons 1

Title

Axis Scales Independent

Variable

Dependent

Variable

Scientific Method: Writing a Conclusion

• Conclusion:

– Completed at the end of an investigation

– Summarizes the purpose and the results of the investigation

– Makes recommendations for future testing

Scientific Method: Writing a Conclusion

In our investigation, we hypothesized that …… During our experiment, we found that ….. Our hypothesis was supported/not supported because…. In the future, we suggest …

For example:We conducted an experiment that answered how weight affects the speed of swings. In our investigation, we hypothesized that if you put more weight in a pirate ship, then the speed of the swings will slow down. During our experiment, we found that the more washers we put in the pirate ship, the faster the pirate ship swung. Our hypothesis was not supported because the pirate ship went faster when more weight was added. This is probably due to the fact that they pirate ship had more energy because of the mass. In the future, we suggest that someone test whether the height of the pirate ship makes the pirate ship ride slow down.

Let’s put our knowledge of the Scientific Method to a realistic

example that includes some of the terms you’ll be needing to use and

understand.

Making ObservationsJohn watches his grandmother

bake bread. He ask his grandmother what makes the

bread rise.

She explains that yeast releases a gas as it feeds on sugar.

Initial Observation Problem/Question

John wonders if the amount of sugar used in the recipe will affect the size of the bread loaf?

Developing a Hypothesis

John researches the areas of baking and fermentation and

tries to come up with a way to test his question.

He keeps all of his information on this topic in a journal.

Developing a HypothesisAfter talking with his teacher

and conducting further research, he comes up with a

hypothesis.

“If more sugar is added, then the bread will rise

higher.”

Doing the Experiment: Identify the Independent Variable

The independent, or manipulated variable, is a factor that’s intentionally varied by the experimenter.

Independent variable: The amount of sugar

John is going to use 25g., 50g., 100g., 250g., 500g. of sugar in his experiment.

Doing the Experiment: Identify the Dependent Variables

The dependent, or responding variable, is the factor that may change as a result of changes

made in the independent variable.

Dependent Variable: the size of the loaf of bread

Doing the Experiment: Procedure/Materials

His teacher helps him come up with a procedure and list of needed materials.

• The materials list must be VERY complete.

• How much of each material will be used in the experiment (25-mL of water or 250-mL of water)

• The size of all equipment (ex 25-mL beaker or 250-mL beaker)

• Every step of the experiment is included

• Each step is short

Then she discusses with John how to determine the control group.

Doing the Experiment: Identify the Control Group

Remember: In a scientific experiment, the control is the group that serves as the

standard of comparison.

The control group may be “no treatment” or an “experimenter selected” group.

Doing the Experiment: Identify the Control Group

Because his grandmother always used 50g. of sugar in her recipe, John is

going to use that amount in his control group.

Doing the Experiment: Identify the Constants

John’s teacher reminds him to keep all other factors the same so that any observed

changes in the bread can be attributed to the variation in the amount of sugar.

What would be some constants for John’s experiment?

Doing the Experiment: Identify the Constants

They might include:1. Other ingredients to the bread recipe2. Oven used3. Rise time4. Brand of ingredients5. Cooking time6. Type of pan used7. Air temperature8. Humidity where the bread was rising9. Oven temperature10. Age of the yeast…etc.

Doing the Experiment: Procedure

John writes out his procedure for his experiment along with a

materials list in his journal. He has both of these checked by his teacher where she checks

for any safety concerns.

Trials

Trials refer to replicate groups that are exposed to the same conditions in an

experiment.

John is going to test each sugar variable 3 times.

Collect and Analyze Results

John comes up with a table he can use to record his data.

John gets all his materials together and carries out his experiment.

SIZE OF BAKED BREAD (LxWxH) cm3

Amt. of Sugar (g.)

1 2 3 Average

Size (cm3)

25 768 744 761 758

50 1296 1188 1296 1260

100 1188 1080 1080 1116

250 672 576 588 612

500 432 504 360 432

Size of Bread Loaf (cm3)

Trials

Control group

Collect and Analyze Results

John examines his data and notices that his control worked

the best in this experiment, but not significantly better

than 100g. of sugar.

Conclusion

John’s hypothesis is unsupported so John rejects his hypothesis, but decides to re-test using sugar

amounts between 50g. and 100g.

ConclusionJohn finds that 70g. of sugar

produces the largest loaf.

Communicate the Results

John tells his grandmother about his findings and prepares to

present his project in Science class.