The Scientific Method

Objectives I will be able to: Identify the different parts of the scientific method Write a scientific procedure Apply the use of the scientific method to common problems

Purpose of scientific method Used to explain things we see

Based on observations about something in the natural world Step 1: Ask a Question Based on observations about something in the natural world

Observations/Identify a Problem Example of an Question- Why do some students have higher test scores than others?

Step 2: Hypothesis A possible answer to the question. Must be testable

Step 2: Hypothesis If independent variable, then dependent variable What is a possible answer to the question, “Why do some students have higher test scores than others?”

Step 2: Hypothesis If independent variable, then dependent variable If students study for more time, then their test scores are higher

A procedure to test the hypothesis. Step 3: Experiment A procedure to test the hypothesis.

Experiment Variable – factor in the experiment that is being tested A good or “valid” experiment will only have ONE testable thing Why?

Independent variable – what I control Experiment Independent variable – what I control

Independent variable – what I control Experiment Independent variable – what I control Dependent variable – what is being measured; depends on changes in the independent variable

Experiment Example: test score and time spent studying Independent variable – time spent studying (I control) Dependent variable – test score (depends on time spent studying)

Experiment Control Group – the group doesn’t get independent variable

Experiment Control Group – the group doesn’t get independent variable Experimental Group – the group(s) being tested; receives different amounts of independent variable

Example Study Time vs. Test Score 5 kids do not study for a test 5 students study for 30 minutes Control Group – the group which is NOT being tested (5 kids that don’t study) Experimental Group – the group(s) being tested (5 students who study)

Example of Controls & Variables For example, suppose you want to figure out the fastest route to walk home from school. You will try several different routes and time how long it takes you to get home by each one. Since you are only interested in finding a route that is fastest for you, you will do the walking yourself.

What are the Variables in Your Experiment? Varying the route is the independent variable (I Control!) The time it takes is the dependent variable Keeping the same walker throughout makes the walker a control variable.

What does your data show? Step 4: Analyze Data What does your data show?

Step 5: Interpret Data & Draw Conclusion Does your data support your hypothesis? Hypothesis can’t be proven! Only supported or not supported!

Retest You can do the experiment many times to make sure the results are accurate.

Step 6: Share Results Share results with other scientists Include very specific procedure Why?

I Do  You like to garden, and notice that some tomatoes are bigger than others and wonder why. You think that one group is bigger because it receives more sunlight than the others. You decide to split the tomatoes up into 2 groups. Everything between the tomatoes is the same, but one group gets no sunlight, and the other gets 6 hours of sunlight a day. You find that the group that gets more sunlight grows larger than the group that receives no sunlight.

I Do Question: why are some tomatoes are bigger than others? Hypothesis:

I Do Question: why are some tomatoes are bigger than others? Hypothesis: if tomatoes get more sunlight, then they grow bigger Independent variable:

I Do Question: why are some tomatoes are bigger than others? Hypothesis: if tomatoes get more sunlight, then they grow bigger Independent variable: amount of sunlight Dependent variable:

I Do Question: why are some tomatoes are bigger than others? Hypothesis: if tomatoes get more sunlight, then they grow bigger Independent variable: amount of sunlight Dependent variable: size of tomatoes Control group:

I Do Question: why are some tomatoes are bigger than others? Hypothesis: if tomatoes get more sunlight, then they grow bigger Independent variable: amount of sunlight Dependent variable: size of tomatoes Control group: tomatoes with no sunlight Experimental group:

I Do Question: why are some tomatoes are bigger than others? Hypothesis: if tomatoes get more sunlight, then they grow bigger Independent variable: amount of sunlight Dependent variable: size of tomatoes Control group: tomatoes with no sunlight Experimental group: tomatoes with sunlight Result:

I Do Question: why are some tomatoes are bigger than others? Hypothesis: if tomatoes get more sunlight, then they grow bigger Independent variable: amount of sunlight Dependent variable: size of tomatoes Control group: tomatoes with no sunlight Experimental group: tomatoes with sunlight Result: hypothesis supported!

We Do  You notice that your friend’s goldfish is much bigger than yours. You both feed it the exact same food in the same amount. You believe that his goldfish is bigger because it lives in a bigger tank. You buy 2 new goldfish, feed them the exact same thing in the same amount and put them in the same water. One is put in a small bowl. The other is put in a big bowl. The one in the big bowl grows to be twice as big.

We Do Question: Hypothesis: Independent variable: Dependent variable: Control group: Experimental group: Result:

We Do Question: Why is one fish bigger than the other Hypothesis:

We Do Question: Why is one fish bigger than the other Hypothesis: If fish live in bigger bowls, then they grow bigger Independent variable:

We Do Question: Why is one fish bigger than the other Hypothesis: If fish live in bigger bowls, then they grow bigger Independent variable: bowl size Dependent variable:

We Do Question: Why is one fish bigger than the other Hypothesis: If fish live in bigger bowls, then they grow bigger Independent variable: bowl size Dependent variable: fish size Control group:

We Do Question: Why is one fish bigger than the other Hypothesis: If fish live in bigger bowls, then they grow bigger Independent variable: bowl size Dependent variable: fish size Control group: fish in small bowl Experimental group:

We Do Question: Why is one fish bigger than the other Hypothesis: If fish live in bigger bowls, then they grow bigger Independent variable: bowl size Dependent variable: fish size Control group: fish in small bowl Experimental group: fish in big bowl Result:

We Do Question: Why is one fish bigger than the other Hypothesis: If fish live in bigger bowls, then they grow bigger Independent variable: bowl size Dependent variable: fish size Control group: fish in small bowl Experimental group: fish in big bowl Result: hypothesis supported!

You Do In Pairs I really like when my mom makes cheeseburgers, but I always feel sick afterwards. I believe the cheese is what makes me sick. My mom makes a new batch of burgers, 5 with cheese, and 5 without. I find that when I eat the regular hamburger, I don’t feel sick afterwards.

You Do In Pairs Question: Why do I feel sick after eating cheeseburgers? Hypothesis:

You Do In Pairs Question: Why do I feel sick after eating cheeseburgers? Hypothesis: If there is cheese, then I’ll get sick Independent variable:

You Do In Pairs Question: Why do I feel sick after eating cheeseburgers? Hypothesis: If there is cheese, then I’ll get sick Independent variable: Cheese Dependent variable:

You Do In Pairs Question: Why do I feel sick after eating cheeseburgers? Hypothesis: If there is cheese, then I’ll get sick Independent variable: Cheese Dependent variable: Sickness Control group:

You Do In Pairs Question: Why do I feel sick after eating cheeseburgers? Hypothesis: If there is cheese, then I’ll get sick Independent variable: Cheese Dependent variable: Sickness Control group: Burgers without cheese Experimental group:

You Do In Pairs Question: Why do I feel sick after eating cheeseburgers? Hypothesis: If there is cheese, then I’ll get sick Independent variable: Cheese Dependent variable: Sickness Control group: Burgers without cheese Experimental group: burgers with cheese Result:

You Do In Pairs Question: Why do I feel sick after eating cheeseburgers? Hypothesis: If there is cheese, then I’ll get sick Independent variable: Cheese Dependent variable: Sickness Control group: Burgers without cheese Experimental group: burgers with cheese Result: hypothesis supported!

Writing a Procedure Procedure is a step by step explanation of how you do an experiment Should look like a recipe

Writing a Procedure Why is a good procedure necessary?

Writing a Procedure Why is a good procedure necessary? So other scientists can recreate experiment exactly!

Tips for Writing Procedure Be very specific Someone should be able to recreate your experiment exactly Number the steps

Tips for Writing Procedure Include units, if necessary Include diagrams, if necessary

Graphing Data

Graphing Data Graphing is used by scientists to display the data that is collected during an experiment

Graph Title Graph title - used to describe what the graph is about

Independent Variable IV – what I control; goes on x-axis

Dependent Variable DV – what you’re measuring; depends on independent variable; goes on y-axis Dependent variable

Scaling Scaling – make each box on your axis worth the same amount

Key key – information telling you what each bar or point means KEY = 1 plant measured

Key

Key key – information telling you what each bar or point means KEY = 1 plant measured

When Should I Use Certain Graphs? Bar graph – when comparing amounts of different groups or times something happens

When Should I Use Certain Graphs? Line graph – shows how things change over TIME

When Should I Use Certain Graphs? Line graph – when independent variable is time