Section 2.1

The scientific method is a means of problem solving using a series of logical steps.

THE SCIENTIFIC METHOD-Section 2.1 1. State the problem2. Make observations3. Formulate a testable hypothesis- a

possible solution or prediction, often written in an “if….. then” format

4. Test the hypothesis using valid experiment

5. Collect Data –chart and graph the data

6. Form a conclusion-accept or reject hypothesis

B. Theories and Laws

1. Theory-explanation of why a phenomenon occurs. Thoroughly tested model with evidence to support it.

Example: Theory of relativity

2. Scientific law-describes an event or phenomenon.

Examples: Newton’s Laws of Motion

II. Setting Up ExperimentsA. An experiment

is a set of steps performed to test the hypothesis and collect data.

1. An experiment can be used to prove or disprove a hypothesis.

B. Designing an experiment: 1. An experiment should have two

types of groups a. The control group serves as a

standard for comparison. It does NOT receive the variable being

tested.

b. Experimental group- receives the element being tested. All other elements must be kept the

same and are called constants or controlled variables. Constants help ensure the validity of an experiment.

*****An experiment may have multiple experimental groups.

The experimental group may receive a placebo (inert substance) to reduce experimental bias.

In a valid experiment all groups must be treated the same except for the experimental group. The elements that are the same for both groups are called constants.

2. Variables are things that change during the experiment.

a. Only one variable is tested in each experimental group at a time.

b. There are two types of variables.

i. Independent variable-also called the manipulated variable. It is what the experimenter uses or changes.

ii. Dependent variable-also called the responding variable. It is the measured change due to the independent variable.

It is what is being measured!!!!

REMEMBER-The dependent variable depends on the independent variable!☺

Waldo’s Experiment

Waldo wants to determine which fertilizer, X, Y or Z, will cause corn plants to grow the fastest. His hypothesis is that the corn plants fertilized with brand Y will grow the fastest because it contains the most phosphorus. What kind of data should Waldo collect in his experiment?

What was the height of plant #5 in What was the height of plant #5 in the Fertilizer Y group on day 15?the Fertilizer Y group on day 15?

Did all groups grow? Which group of plants had the

greatest growth? What might you conclude about

using fertilizer v.s. not using fertilizer

Practice Problem

A pharmaceutical company gets FDA approval to test a memory medicine on humans. The pharmaceutical company chooses 100 participants and splits them into two groups of 50 each. Once a day and over a period of 6 months, each participant is given a pill. In one of the groups, the pill contains the medication. In the other group, the pill contains no active ingredients. One a week, the participants are given a test that measures their memory. The score for the test is recorded each week.

What are the test scores recorded in this experiment over the 6 months time called?

Which group of participants represents the control group?

The pill containing no active ingredient is called a-

Which of the following would NOT be an effective added control for this experiment?

Testing each participant the same day and same time every week.

Testing each participant’s memory for one month prior to conducting the experiment.

Controlling the diets of the participants so that they eat the same types of foods.

Controlling where each participant shops for groceries each week.

Which of the following would MOST effectively reduce the effect of the bias of the pharmaceutical company that developed the medicine?

Create an additional experimental group to test a different dosage of the medicine.

Have an independent researcher to administer the pills and perform the tests.

Decrease the number of participants in the experiment by half.

Increase only the number of participants receiving the medicated pills.

What would be an effective control for this experiment?

Testing and recording each participant’s memory over a period of time BEFORE conducting the experiment.

Determining the average memory tests for the general population apart from the participants.

Testing the memory of each participant after he or she watches 4 hours of television

Recording memory scores for family members with participants.

Which of following is the dependent variable?

6 months time The memory enhancing medication The change in memory The pills with no active ingredient

Practice Problem

A strawberry farmer conducted an experiment to test the optimum pH level of soil to give the greatest production of strawberries. He believed that the optimum pH would be around 5.5. For each pH level, he recorded average pounds of strawberries produced per plant and total pounds of strawberries produced per acre. His results are as follows:

At ph level of 6.0, how many pounds of strawberries per plant are recorded?

Write a statement that describes what happens to stawberry production as pH levels change?

What is the best pH level for optimum strawberry production?

If a pH of 7 neutral, values below 7 are acidic, and values above 7 are alkaline, how would you characterize the best soil for growing strawberries?

Based on the data, which of the following choices is the BEST conclusion?

Accept the hypothesis that optimum pH is 5.5

Reject the hypothesis that the optimum pH is 5.5

Support the theory that the optimum pH is 5.5

Reject the theory that the optimum pH is 5.5.

Are all of the groups of plants growing?

Can you tell which group is showing the greatest increase in height?

How would you rank the growth of each group as compared to the others?

On what day were the average heights of the Fertilizer X group and Fertilizer Y group the same?

Does this graph support Waldo’s Hypothesis?

III. Using Tables to Organize and Interpret Data--Section 2.3 A. Tables organize and present date

in both quantitative and qualitative forms. i. Qualitative data- detailed description ii. Quantitative data--numerical data

B. Always title, label, and show units of measure in a table.

IV. Using Graphs and Diagrams to Organize and Interpret Data--Section 2.4 A. Graphs are visual interpretations

of data. Types of Graphs Include: 1. Line Graphs 2. Bar Graphs 3. Pie Graphs

B. Line Graphs

1. Often used to show changes over time.

2. x-axis is the independent variable; while the y-axis is the dependent variable.

3. Variables are numeric measurements.

4. Line graphs allow you to see the following trends.

1. Upward Trends

2. Downward Trend

3. Peaking Trend

4. Unstable Trend

Line graphs must contain:1. Title2. x and y axes that are properly

labeled.3. x and y axes showing the proper

unit of measurement.4. Proper scale and range

D. Bar Graphs Present groups of data that are

not continuous. Show different amounts or

quantities among different groups.

One variable is non-numeric.

E. Pie Graphs (Circle Graphs) Used to show percentages of a

whole. Slices represent the parts of the

whole. The whole is total or 100%

F. Diagrams

Labeled pictures to show relationships between objects or parts.

Give general information. Communicate experimental

data.