What is the Scientific Method?

Where Are We Starting?
Welcome to Biology and to High School! Most of you have gone to one of four different schools. So,
our goal today is identify what you remember about what you were taught in Middle School
Each of you has five different color cards. Write your answer (one answer per card) in letters large
enough that everyone can read it when you put it on the bulletin board. (Use the magic markers and
Yellow Cards: Name one thing that you learned in Middle School that you would consider “biology”
Pink Card: Often scientists use a method or process to study science. Can you name this process?
Orange card: Name the steps that you remember in this process (in order)
Blue card: What are two living things you study in Middle School?
Green card: What characteristics can you think of that ALL living things must have in order to be
“alive” ?
Answer the next two questions in the space below each question.
1. What science have you studied that is not Biology. How would you define science?
2. What does it mean to scientifically study things in other words, how do we “do” science?
Intro to Biology -2 How We Study Science
What is Science
Science is a word that we use to describe the method or means by which humans try to understand the world
around us. We do this by using a combination of two basic approaches
1. Discovery Science (Descriptive Research)
a. We observe some phenomenon
b. We record what we see, measuring when possible
c. We make sure that what we see happens over and over again
d. Ideas are developed to understand the observation (we “tailor” our idea to what we see)
2. Hypothesis-driven Science (Experimental Research)
a. Discovery Science starts this type of science, BUT
b. We develop an idea (first) and predict what should happen
c. Uses the scientific method (an organized, rational approach to problem-solving) to test a
hypothesis, which means altering a variable in the known system and seeing what happens – the
result will either prove or disprove your hypothesis.
d. We judge the “goodness’ of our prediction based on the designed experiment.
Experimental science can often be categorized as either pure science or applied science. Pure science, also
known as "basic science," tries to answer basic questions about reality, such as the nature of aspects of the
physical universe, the mechanisms of life, or the workings of the mind. Pure science isn’t conducting with an
application or product in mind. Examples include trying to understand the structure of a molecule, how a cell
works, or how groups of people become more cohesive or divisive are all questions of basic science.
Applied science tries to solve a specific problem or set of problems, or to create a product. Developing a better
solar panel to generate less expensive electrical power involves applied physics and chemistry. Creating a
treatment to prevent or cure a disease is applied biology. Applied science is used to make discoveries that
improve living conditions (there is an application or product in mind).
Intro to Biology -2 How We Study Science
What is the Scientific Method?
1. Make observations regarding some phenomenon (either directly, or using the knowledge of others.
2. Ask a question based on your observation
3. Create a statement that you believe explains the generalization (hypothesis)
a. Must be testable and measurable
4. Design an experiment to test the hypothesis. Your measurements and procedures should have
operational definitions if they might be interpreted differently by different people.
5. Conduct the experiment
6. Record results (observations and measurements)
7. Conclude, based on results. Conclusions are made by inferring from the data you have gathered and
your previous knowledge. Conclusions can support your hypothesis or lead to an new hypothesis.
8. If a hypothesis is tested in many ways, but is not disproved, it can become a theory
Let’s review each vocabulary word through some activities, to ensure we all have the
same definition.
When you observe, you use one or more of your senses. Identify a “scientific” observation that you
could make with each of your five senses. .
Think about the observations you have written. Is your observation accurate and objective? Accurate
means that it is correctly recorded (you don’t interpret, just report). Objective means that it avoids a
certain point of view (we call this bias). Look at the next three statements. Which is not objective?
Which is not accurate? Which is accurate and objective?
a. It is raining.
b. It rains all of the time!
c. The weather is awful.
Additionally, your observation can be either qualitative (described by words and not numbers) or
quantitative (observations that include numbers). “Three centimeters of rain fell between 10am and
11 am today” is an example of a quantitative observation. In science, you often use tools (balances,
Intro to Biology -2 How We Study Science
microscopes, rulers, graduated cylinders) to make quantitative observations. Circle the quantitative
statements below.
The plant’s leaves are dark green
The plant has long , thin leaves
The plant grew 5 centimeters during the week.
Three grams of fertilizer were applied to the plant today
Finally, be sure you understand the difference between an observation and an inference (also called an
interpretation). An accurate observation is a correct, factual statement, while inference is a judgment
based on observation and past experience. Inferences are not always correct. Be sure that what you
write as an observation, is not an inference. Identify the observation and the inferences.
a. This rock has a smooth surface
b. The school band will probably meet after school as usual
c. The band members must need extra practice after school to learn their new songs
Use the illustration to answer the questions
that follow.
1. Make three qualitative observations
about the photograph
2. Make two quantitative observations
about the photograph
What are two inferences that you could
make. What evidence do you have that
supports your inferences?
Intro to Biology -2 How We Study Science
Why is it important to differentiate between observations and inference? An observation can be
interpreted many ways. In your conclusion you may believe that the data infers one thing, while your
classmate may believe it infers something else. It is important that others be able to identify what you
observed and separate it from your conclusions. Making an inference means choosing the most likely
explanation from the facts at hand. Inference is used when we make a conclusion or judgement
Because of this, written observations are included in the data section of formal lab report. Inferences
are reserved for the discussion/conclusion section of the same report. Scientists are not the only ones
to do this. Consider the following situation:
Suppose you are sitting in your car stopped at a red signal light. You hear screeching tires, then a
loud crash and breaking glass.
What do you observe?
What would you infer?
What would you tell a police officer if he asked you what happened?
Intro to Biology -2 How We Study Science
Newspaper Article
Read the article Stony Bacteria. Make a list of what the scientists actually observed. What
inferences were made based upon this data?
What conclusions can you make based upon the information in this article?
Intro to Biology -2 How We Study Science
Intro to Biology -2 How We Study Science
Intro to Biology -2 How We Study Science
My grandmother was an excellent cook and I learned much about cooking from watching and helping
her. BUT, my grandmother’s method of measuring had to be “seen” to be understood. Her
measurements included “butter the size of an egg”, salt to taste, a dash of pepper, and 2-3 handfuls of
flour. Most of the time, she would just add things until it looked right or tasted right. She had similar
directions for “how to cook”. For example: cream butter and sugar, beat until frothy, and “beat till
soft peaks form”, add flour until dough is the right consistency and cook in an oven at medium heat.
My grandmother never had problems “repeating” her own recipes, but when others asked for a recipe,
their brownies or cake were never quite the same as Grandma’s.
So, why do you think that it was difficult for others to produce the same moist, chewy brownies that
my Grandma made? Think about her “measures”.
How many tablespoons are in a lump of butter which is the size of an egg?
What measure equals a “dash” of pepper?
How many cups are 2-3 handfuls?
In terms of procedures:
What does cream butter and sugar mean?
What does frothy mean?
And what is medium heat?
When we work in the lab, we are often using a procedure written by someone else. When that person
writes a procedure, they are, in reality writing something that is similar to a recipe. If we are trying to
replicate an experiment, it is important that we have specific directions or procedures, so that we can
do the experiment in the same way. When we don’t replicate the amounts and the procedures, we
may obtain different results.
Cookbooks were written to provide standard recipes that had measures and instructions for how to
measure (level the flour by scraping off the excess flour with a knife) and how to combine ingredients.
Operational definitions are very important for consistency. Let’s deal with measures (and calculations)
first, and then work on operational definitions. When you measure, is important to choose the RIGHT
tool for whatever we are measuring. On the next page are various tools and measures that we might
use for liquids and solids. Additionally we will use a ruler (generally cm or mm) or a balance (grams).
Intro to Biology -2 How We Study Science
Common laboratory equipment (including measurement tools)
We will most often measure liquid using a graduated cylinder. It is important to use the “right size”.
We have 10 ml, 100 ml, and 500 ml graduated cylinders
Beakers are utilized for reactions or to pour reagents from. They are NOT used to measure. Generally
flasks will be utilized for the same purpose. Again, use a size that is appropriate for the task. Finally,
we will use test tubes when the reactions (or amount of reagent) is small, and we want to be able to
examine the reactions “up close”.
Goggles MUST be used for all experiments using glass or reagents!
Intro to Biology -2 How We Study Science
When you make measures, consider the following:
1. Determine which unit is appropriate for the measurement you are making and “how large” the
container or measurement device needs to be.
2. Select the right tool for the measurement
a. If you a measuring 5 ml, you need a 10 ml graduated cylinder, NOT a beaker or a 100 ml
graduated cylinder
b. If you are measuring your height, a meter stick will work better that a small ruler.
3. Be sure that you understand the units that are found on the measuring device. If you are using
a balance, make sure that you place your “dish” on the balance FIRST and tare it (zero it) so that
your measure actually represents the mass that is IN the container and not the mass + the
4. Always measure as precisely as possible. If a graduated cylinder is marked in ml. you should be
able to estimate to the nearest 0.5 ml. If you are using a rulers that is marked in mm, you
should be able to estimate to the nearest 0.5 mm.
5. When calculating, make sure that the measures use the same units and that all calculations are
labeled with units.
Identify the glassware and measuring tools found on your lab table (in “letter order”)
Complete the Skills Practice for Measuring: Length; Measuring: Liquid Volume; and Measuring
Create and label a data table (in the space below) that identifies the Line (A,B,C) and the measurement
in mm and cm for your measurements on the first page of the Skills Practice for Length. Use a ruler!
Intro to Biology -2 How We Study Science
Intro to Biology -2 How We Study Science
Intro to Biology -2 How We Study Science
Intro to Biology -2 How We Study Science
Intro to Biology -2 How We Study Science
Intro to Biology -2 How We Study Science
When completing labs, you will often be asked to utilize your measurements and make some type of
calculation or create a graph.
One common kind of calculation in science and math is determining rates. One definition of rate is the
speed at which something happens. For example, you may need to know how often something occur
per minute, or determine the growth of a plant per day.
Rates are used by ecologists to determine birth and death rates. Rates are utilized by chemists or
biologists to determine how rapidly a reaction occurs. If you know the rate at which something
happens, you can use this information to determine how often something happens in any given time
period. For example, you check your pulse and determine that there are 20 pulses in a 15 second
period. You are now asked to determine your pulse rate per minute. To determine this, you need to
CONVERT the time unit you have into minutes.
Conversion is accomplished by multiplying by a term that is equivalent to 1, but contains both the unit
you start with and the unit you wish to end with. For example: 1 minute = 60 seconds.
20 pulses
15 seconds
We want to replace seconds with minutes. If we multiply this rate by 60 seconds
1 min
You can cross out “seconds” and are left with
1200 pulses
15 min
80 pulses
1 min
When asked to do calculations, show work, and each step of the calculation. Be sure you show units
and the conversion factor. Make sure your final answer is labeled with the correct units.
Complete the Skills Practice: Calculations
Intro to Biology -2 How We Study Science
Intro to Biology -2 How We Study Science
Graphs are utilized to help interpret data. Graphs are utilized so that patterns in the data can be seen.
Patterns help us to understand how the dependent and independent variable are related.
Data should be placed in a table (or in a spreadsheet) before attempting to draw a graph. It is
important to order the data in the table so that it best addresses the question you are trying to answer.
Example: Suppose that a scientist is measuring the speed that sound waves travel at different air
temperatures. An experiment was performed, and data were gathered on different days . All
temperatures are in oC.
Speed of sound (m/s
June 5
July 19
Aug 5
Oct 1
Oct 10
Jan 20
What question is the scientist trying to answer?
Which two columns of data are most important in answering the question
Which measure DEPENDS on the OTHER VARIABLE?
Rearrange the data in a table
Intro to Biology -2 How We Study Science
Graph Title
Variable on Y axis:
Variable on X axis:
Which variable, X or Y is dependent variable? (it DEPENDS on the setting of the other). Which variable
is the INDEPENDENT variable?
Be sure to name the graph AND name the table and label the two axes (with the UNITS)
What number did you choose to start each axis? Why ? What type of graph did you choose? Why?
Graph the data. What can you conclude (or infer) from your graph?
Intro to Biology -2 How We Study Science
On Your Own
Number of Frog Croaks at Different
Temperature C
Write a sentence that summarizes the data.
What is the difference between the greatest number of croaks measured in a minute and the least
number of croaks measured in a minute?
What was the greatest temperature at which information about frog croaks was collected?
What number of croks would you expect to hear if the temperature were 21 C? Why?
Eoes the number of frog croaks increase the same amoun for each degree of temperature increase?
Write a sentence that describes any trends you note in the data.
Intro to Biology -2 How We Study Science
In science, exact definitions are important. An exact definition allows scientists to repeat teir own
work and the work of others. An operational definition is a statement that describes how a particular
variable is to be measured, or how an object or condition is to be recognized. The word operational
means “to describe what to do”). Operational definitions are used whenever a term doesn’t have a
clear single meaning.
Let’s go back to some of grandma’s “how to cook” (demonstration
Cream butter and sugar
What does “cream butter and sugar” mean? Should the butter be soft or hard? What tool
should we use to do this? If we are using a mixer, what speed do we use (and what size
Separate eggs and beat whites until frothy,
How do you separate eggs? Is there an “average beat time”, or a set amount of froth?
“Beat till soft peaks form”
What is a soft peak? Beat with what?
Add flour until dough is the right consistency for rolling .
What is the right consistency?
Should we at least provide a “rough measure” of flour?
Cook in an oven at medium heat.
What does medium heat mean? Should you preheat?
Intro to Biology -2 How We Study Science
Suppose you are conducting an experiment to determine how air temperature in a room affects the
growth rate of plants. If the lab report said “some of the plants were kept in a cold room, while others
were kept in a warm room”, you would not be able to repeat the conditions of the experiment. The
words cold and warm do not have a single clear meaning. An operational definition should be used in
your lab report. A statement such as “some of the plants were kept in a room with an air temperature
of 10 C and other plants were kept in a room with an air temperature of 30 C”, would have the
information that you needed to repeat the experiment’s conditions.
Operational definitions are also used to describe how variables are measured. In the
experiment described above, we are measuring the growth of a plant over time. So a lab report must
include how the rate of plant growth was determined.
EXAMPLE: The height of the plants was measured once every 24 hours using a centimeter ruler. The
height was measured to the nearest centimeter. The change in height was determined by subtracting
the previous day’s height from the current height. The rate of growth was reported based on change
in centimeters per day.
When you write an operational definition, make sure it describes what to do or what to observe. Be
sure that any terms in your lab report that do not have a single, clear meaning have an operational
definition. Here are some examples of operational definitions.
1. The maple tree population in an area of 100 square meters increased compared to last year.
OPERATIONAL DEFINITION: The maple tree population in an area was determined by counting
the number of maple trees in one tenth of the area and multiplying that number by 10.
2. Cut flowers stay fresh longer if they are kept in warm water (70F) than they do if they are kept
in cold water (45F).
OPERATIONAL DEFINITION: Fresh: cut flowers are considered “fresh” if they have not lost any
A good operational definition should also tell how frequently a particular measurement is made.
1. If an experiment requires the measurement of the temperature of a beaker of water as it heats
over a flame, the operational definition might be: the temperature of the water is measured in
o C at 5 min intervals, using a thermometer.
Intro to Biology -2 How We Study Science
SUMMARY: Operational Definitions should be:
Written as you plan your investigation or experiment
Written when a term does not have a single, clear meaning
Used to clarify methods used to measure variables
Used to allow someone to duplicate your work
Be checked by someone to ensure the directions are accurate.
Complete Worksheet: Forming Operational Definitions
Intro to Biology -2 How We Study Science
Intro to Biology -2 How We Study Science
Do Inquiry Activity 1:
Why Does the Cup “Blow Up”
These experiments represent a well-known Physics Principle. Find a SCIENCE website (NOT WIKI
ANSWERS or WIKIPEDIA) that explains why this happened and identify the principle. Copy and paste
the website below and explain briefly (in your own words) on the next page why all of the results you
obtained support this principle. (Use another piece of paper!
What is this principle and how do your results support this experiment?
Intro to Biology -2 How We Study Science
1. Look over the material we have covered to date. Go back to page 2 and look at the terminology
that we have discussed and reviewed. A good check to determine whether or not you
understand the vocabulary is to write a “new story” using all of the words (in any order). Work
in your lab groups to write “sequential sentences” (to tell a story). Start the story (put a
sentence on an index card). If the statement correctly uses the vocabulary word or words, the
next person adds a second sentence. As the number of sentences increase, you may “insert”
sentences, rather than just “put them at the end.”
Operational definitions
2. In our first experiment “Why Does the Cup Blow Up” the observations were qualitative and not
quantitative. A. Explain what this statement means and B. suggest two measurements that we
might have been able to make (if we had the proper equipment) to quantify our observations.
C. Write an operational definition for each measure.
3. Is this inquiry activity discovery science or hypothesis driven science. Explain
4. If you redid the experiment using your new measures (identified in #2), how would the
“materials list” required for your lab group to conduct this experiment change? . Include all
Intro to Biology -2 How We Study Science
So far, we have “asked a question”, restated that question in an “IF…THEN” structure,
recorded observations, made inferences, and formulated a “new hypothesis”. We have
discussed how to write procedures for measures and experimentation (operational
definitions) and talked about the difference between qualitative and quantitative
The experiment that we conducted was actually actually “discovery science”. Many
times we do this type of experimentation as a precursor to “designing an experiment” to
test a hypothesis.
Designing an experiment involves putting all of the above steps together in steps that
we call the experimental method. When the scientific method is utilized to answer
questions, experimentation has to be highly organized and controlled to have any
Since many things (we call them variables) can affect the outcome of the experiment, it
(the experiment) should be designed so that there is potentially only a single
explanation for the results. The variable that is being tested (the variable you think
affects the outcome of the experiment) is known as the independent variable (also
called the manipulated variable). The variable that we believe will change in some way
when we change the level of the independent variable is called the dependent variable.
Your hypothesis is always stated in terms of the effect of some level of the independent
variable on the dependent variable.
Look at the worksheet entitled “Experimental Scenarios”. Identify the independent
variable and the levels of the independent variable in each scenario. Then define the
dependent variable and write a possible hypothesis. If you can do this successfully, you
are now ready to design your own experiment!
Intro to Biology -2 How We Study Science
1. Breakfast Cereal Iron
Natalie wants to know how much iron is contained in a cup of two popular breakfast cereals. She put a cup
of Total and a cup of water into a bowl. She then put a cup of Corn Flakes and a cup of water into another
bowl. She let each bowl set for 24 hours. The next day Natalie inserted a magnet into each cup and stirred it
around. She measured the amount of iron filings in milligrams from each cereal.
2. Teaching Fish Through Association
Ellen wanted to see if fish could “learn” by association. She set up two identical ten-gallon aquariums. The
walls and tops were covered with black construction paper to prevent light from entering. Ten feeder
guppies were added to each aquarium as test subjects. A small corner of each aquarium was left open, and
a small reading light is placed over it. In tank 1, the light is turned on over the aquarium, and thirty seconds
later, a small amount of food is added to the tank. Tank 2 is a control, and no food is added after the light is
turned on. After a week of this, Ellen counts how many fish swim to the light when it is switched on.
3. Acids and Bases
Billy wanted to find out if certain liquids were acids or bases. He used lemon juice, water, and glass cleaner
for samples. The water was used as the control. He placed two tablespoons of each liquid into separate
beakers. Then he took three strips of red Litmus paper and dipped one into each beaker then laid them out
to dry. When they dried, he then recorded the color of the paper and whether it was an acid or a base. A
positive base test is blue, a positive acid test is red, and in a neutral test the paper does not change.
4. Color and the Food Choices of Children?
Sandy wanted to find out if the color of a food would affect whether or not kindergarten children would
select it for lunch. She put food coloring into 4 identical bowls of mashed potatoes. The colors were red,
green, yellow, and blue. Each child chose a scoop of potatoes of the color of their choice. Sandy did this
experiment using 100 students. She recorded the number of students that chose each color.
5. Effectiveness of home insulation
Esther became interested in insulation while her parent's new house was being built. She decided to
determine which insulation was best. She filled each of 5 jars half-full with water. She sealed each jar with a
plastic lid. Then she wrapped each jar with a different kind of insulation. She put the jars outside in the
direct sunlight. Later, she measured the temperature of the water in each jar.
Intro to Biology -2 How We Study Science
Designing Your Own Experiment
Every experiment has parts that you should be able to identify. When you are designing
an experiment you should refer to the General Layout for an Experimental Design
Diagram (in the reference section) to ensure that you have included all parts in your
design OR to verify that you have correctly identified all components if you are
conducting and analyzing a previously designed experiment.
When designing an experiment, there are key variables that will be important in an
experiment. Suppose that you want to look at the germination (sprouting) and growth
rate of two different species of plants (corn and beans). It is fall, so you need to grow
them indoors. You need to have all important variables “the same”, except for your
“experimental variable” (independent variable) and have a “dependent variable’ (one or
more) that are measurable. You will also want to repeat an experiment (or a test within
an experiment) for verification (repeat or repletion).
Three Stages of Germination Beginning plant growth
Mature plant w/ seed pods
The pictures above show potential “ benchmarks” for growth. Use the Layout for an
Experimental Design template on the next page to identify key factors and
measurements in your experiment. Think about how you will keep important factors
Intro to Biology -2 How We Study Science
General Layout for an Experimental Design Diagram
TITLE: The effect of ______________________________(Independent variable) on
__________________________ (Dependent variable.
HYPOTHESIS: If I __________________________ (list the change in the independent
variable) then _______________________________( how will the measurement of the
dependent variable change) .
INDEPENDENT VARIABLE: _________________________________________
possible) and at least one other level, or at least two levels.
Level 1
Level 2
Level 3
Level 4
Level 5
DEPENDENT VARIABLE(s): __________________________________
How will you measure _____________________________________________
WHICH VARIABLES SHOULD YOU KEEP CONSTANT (name those that you believe could
most affect the dependent variable besides the independent variable)?
Intro to Biology -2 How We Study Science
In addition to just “stating the words”, it is often a good idea to draw a picture of the experiment you have just
designed. Draw a PICTURE of the experiment you have outlined in the previous exercise and label the
dependent variable and its levels, the independent variable, the constants and the control.
Intro to Biology -2 How We Study Science
So, if I asked you to design your own experiment right now, would you be able to come up with a specific topic
for an experiment? It is easier to come up with a general topic, but it is not as easy to translate this general area
into a focused topic for study.
You can use a four question strategy to explore possible variations of a general topic before attempting to state
a specific problem, hypothesis, variables, constants, and a control. When we teach students the process of
experimental design, we should model and practice this four-question strategy with students BEFORE asking
them to design an original experiment on his own. The teacher can lead the students in the class through one
example of the four-question strategy, all together, using the chalkboard. The students can then practice the
four-question strategy alone or in small groups, using a prompt provided by the teacher, before attempting to
work through the four questions for an experiment that they are interested in carrying out.
The four-question strategy involves the following four questions:
What materials are readily available for conducting the experiments on the general topic of interest
What action is observed when studying (the general topic of interest).
What are all the ways I can change the set of materials that would change the action
In what ways can I measure or describe the response or change.
A specific experiment follows from the answers to the four question strategy. One of the answers to question 3
will be the independent variable in the experiment. All the other answers to question 3 (other things that could
be changed to create an effect) need to be controlled (set at a constant value) when the experiment is
conducted. They will become the constants of the experiment. The answer to question 4 will become the
dependent (response) variable of the experiment.
The following example of the four question strategy might be answered using the general topic of plants.
1. What materials are readily available for conducting experiments on plants
a. (soil, plants, fertilizer, water, light/heat, containers)
2. How do plants act (plants grow)
3. How can I change the set of plant materials to affect the action (growth)a. Plants, spacing , kind, age , size,
b. Water: amount, scheduling, method of application, source, composition, pH
c. Containers: Location of holes, number of holes, shape , material, size color(possible changes in soil,
fertilizer, and light/heat would also be listed)
4. How can I measure or describe the response of plants to the change?
a. Count the number of leaves
b. Measure the length of the longest stem
c. Count the number of flowers
d. Determine the rate of growth
e. Weight the fruit produced
f. Measure the diameter of the stem
Intro to Biology -2 How We Study Science
Once students have carried out the four-question strategy, they should be asked to create an experimental
design diagram for an experiment that they could carry out based upon their answers. Once they have
constructed an experimental design diagram, the student will be ready to proceed with writing an experimental
procedure to follow for their experiment.
It will often be helpful for the teacher to help students further in beginning the experimental design process by
providing a prompt to help the students begin the four-question strategy activity. You can provide the students
any of the following as a starting point for them to begin the four-question strategy.
Lists of simple and available materials
Questions to be investigated
News briefs or articles that lend themselves to further experimentation by students
Science demonstrations in a book
Textbook or laboratory activities
Library book
Whatever the type of prompt used it should stimulate student interest and curiosity.
Intro to Biology -2 How We Study Science