1. THE SCIENTIFIC METHOD
Regents Biology

2. Upon completion of this unit students will be able to:
OBJECTIVES
Upon completion of this unit students will be able to:
1. List, in order, the steps of the scientific method.
2. Write a formal hypothesis using the IF…THEN format.   
3. Explain the differences between each of the following variables:
Independent
Dependent
Controlled
4. Explain what is meant by a controlled experiment.
5. State the importance of a control group in an experiment.
6. Given an example, identify the control group and the experimental
group; the independent variable, dependent variable, and controlled
variable.

3. KEY TERMS control group dependent variable experiment hypothesis
KEY TERMS
control group
dependent variable
experiment
hypothesis
independent variable
scientific method

4. I. THE SCIENTIFIC METHOD
In this course you will be observing many living organisms and phenomena and asking questions about them. All scientific investigations use a general format for answering questions, which is called the SCIENTIFIC METHOD.
This is the UNIVERSAL approach to conducting scientific experiments.
Scientists in ALL fields approach their problems in the same way using the scientific method. When a scientist announces a finding or proposes a new idea, other scientists may REPEAT THE WORK OR TEST THE FINDINGS TO VALIDATE THE EXPERIMENT, which creates the need for a universal method.

5. A. STEPS OF THE SCIENTIFIC METHOD
1.Identifying a PROBLEM or Asking a QUESTION
 2.Stating a HYPOTHESIS
 3.TESTING the hypothesis designing a controlled EXPERIMENT
 4.COLLECTING and RECORDING data
 5.REVIEWING your results
6.Coming to a CONCLUSION as to whether your HYPOTHESIS is supported or refuted

6. If a scientist’s hypothesis is refuted, then he/she will REDESIGN THE EXPERIMENT OR TEST SOMETHING DIFFERENT THAN ORIGINALLY TESTED
II. CONDUCTING A SCIENTIFIC EXPERIMENT
A. IDENTIFYING A PROBLEM OR ASKING A QUESTION
This is where the scientist IDENTIFIES A PROBLEM and searches for information relevant to the topic
Scientists usually put the problem in the form of a QUESTION to begin an investigation or topic of research

7. B. STATING AND WRITING A HYPOTHESIS
A hypothesis is an EDUCATED GUESS that suggests a possible explanation of an observed set of facts.
A useful hypothesis is TESTABLE and may include a prediction. The key word is TESTABLE.
Scientists look at PATTERNS in the existing data when they make a hypothesis.

8. These “factors” are called VARIABLES.
Throughout the year you will be asked to perform a test to see how two or more VARIABLES might be related. This is when you are doing a REAL experiment. You are stating a HYPOTHESIS and testing VARIABLES
Any laboratory procedure that you follow without a hypothesis is NOT an experiment. These activities are exercises or demonstrations of what is already known.

9. A hypothesis is either SUPPORTED OR REFUTED
A hypothesis can NEVER be PROVEN because at any time, a hypothesis can be refuted by NEW RESULTS

10. A hypothesis uses AN “IF…THEN” statement:
Examples:
IF skin cancer is related to ultraviolet light, THEN people with a high exposure to ultraviolet light will have a higher frequency of skin cancer.
IF leaf color is directly related to temperature, THEN exposing plants to low temperatures will result in changes of leaf color.

11. The ultimate value of a formalized hypothesis is that it forces you to think about what RESULTS YOU SHOULD LOOK FOR IN AN EXPERIMENT
PRACTICE
Directions: Rewrite each of these statements into formalized hypotheses.
 1. Chocolate may cause pimples.
2. Salt in soil may affect plant growth.

12. C. DESIGNING A CONTROLLED EXPERIMENT: VARIABLES
Generally speaking, this involves the MATERIALS AND METHODS, what materials the scientists is using and how he/she is going to use it; the design of the experiment.
Experimenting is the process of testing a hypothesis by gathering data under CONTROLLED CONDITIONS

13. A controlled experiment compares a DEPENDENT VARIABLE with an INDEPENDENT VARIABLE
More specifically, a controlled experiment involves the two variables in your formalized hypothesis. One is the DEPENDENT VARIABLE and one is the INDEPENDENT VARIABLE

14. 1.  THE DEPENDENT VARIABLE
The dependent variable is what the investigator MEASURES, COUNTS, OR RECORDS. It is what the investigator thinks will be affected during the experiment.
Example: Consider a study on the growth and development of fruit trees. Can you think of any measurable characteristics you could use to determine whether or not a plant is growing?
 1.  _____________________________
 2.  _____________________________
 3.  _____________________________
 4.  _____________________________

15. For any experiment, there may be a number of possible dependent variables. The investigator must choose the one that is the most important.
If you are given a set of variables and are having trouble identifying the dependent variable, ask yourself the question:
WHAT DEPENDS ON WHAT?

16. Examples: Let’s circle the dependent variables in the given sets:
 time (months) and growth (cm)
amount blood (mm) and acidity of cells (pH)
height of tree (in) and amount of rainfall (in)
 pulse rate (beats/minute) and time (min)

17. 1. THE INDEPENDENT VARIABLE
The independent variable is the ONE thing that investigator CHANGES or MANIPULATES during an experiment. It is what the investigator thinks will effect the dependent variable.
All of the things that we DID NOT circle on the previous page are independent variables.

18. Example: Consider the study on the growth and development of fruit trees. Name some factors that might affect the growth of a fruit tree:
 1.     ______________________________
 2.     ______________________________
 3.     ______________________________
  ______________________________

19. Unlike the dependent variable, the investigator must choose only ONE independent variable to do a scientific investigation.
Example: If you want to investigate the effect of a fertilizer on the growth of fruit trees, you would use different amounts of fertilizer on different fruit trees. Because you are varying the amount of fertilizer given to each plant, it is the INDEPENDENT VARIABLE

20. REMEMBER:
THERE MAY BE SEVERAL DEPENDENT VARIABLES, BUT THERE MAY BE ONLY ONE INDEPENDENT VARIABLE

21. Since there can only be ONE independent variable, all other independent variables other than the one being studied must be IDENTICAL or remain constant in all subjects and trials throughout an experiment.
All of the variables that MUST remain the same throughout the entire experiment are known as the CONTROLLED VARIABLES

22. Since the investigator wants to study the effect of ONE particular independent variable, he or she must eliminate the possibility that other factors are effecting the outcome.
Example: Consider the study on the effects of fertilizer amount on the growth of fruit trees. You must be sure that there are NO DIFFERENCES in the type of fertilizer used.
How could this be done?
What other things have to be controlled (remain the same) by the investigator?

23. **SCIENTISTS SPEND MOST OF
TYPES OF VARIABLES
INDEPENDENT
DEPENDENT
CONTROLLED
amount of fertilizer
fruit tree growth
**SCIENTISTS SPEND MOST OF
THEIR TIME MAKING SURE THAT ALL OF THE CONTROLLED VARIABLES REMAIN CONSTANT THROUGHOUT AN ENTIRE EXPERIMENT**

24. 1.  THE CONTROL GROUP VS. THE EXPERIMENTAL GROUP
A controlled experiment also involves a CONTROL GROUP
When the duplicate setup is made there is one factor changed in one setup (EXPERIMENTAL GROUP) and no changes made in the other (CONTROL GROUP)

25. The control group is used as a REFERENCE for comparing data and is important because it allows the investigator to be sure that the effect on the dependent variable (fruit tree growth) is in fact due to the independent variable (fertilizer). It is also commonly known as BASELINE data
Example: In the fertilizer and fruit tree experiment, the control group would be a set of plants in which the independent variable (fertilizer) is eliminated.

26. D. ORGANIZING AND COLLECTING DATA
This involves recording PRECISE and ACCURATE procedures that the scientists does, and observations made
Observations involve using the 5 senses and can utilize tools for precise and accurate data collection
Data is usually reflected in a TABLE, GRAPH OR CHART for easy interpretation

27. ·        This is the LONGEST phase of an investigation
Most scientific observation in science involves QUANTITATIVE data, which is data that can be measured in NUMBERS; data can also be QUALITATIVE which is more or less DESCRIPTIVE

28. REVIEWING/ANALYZING RESULTS
From the “hard core” data, results are analyzed and then stated, but not interpreted or discussed yet.
This is the section where STATISTICS is usually used to determine whether data is reliable and whether it supports a hypothesis or not.

29. F. CONCLUSION
Conclusions must be supported from the experimental DATA and RESULTS
If there any deficiencies in any part of the scientific method, the scientists’ work is REJECTED and not published
A good experiment is one that can be REPEATED and others get the SAME results

30. Theories are explanations that apply to a broad range of phenomena; a hypothesis that is supported REPEATEDLY becomes a theory
Scientists learn from each other; they SHARE results and information, which allows scientists to build on the work of each other.