1. Solving Problems—Identify
the Problem
• Although the investigation of each problem
is different, scientists use some steps in all
investigations.
• Scientists first make sure that everyone
working to solve the problem has a clear
understanding of the problem.
• Sometimes, scientists find that the problem is
easy to identify or that several problems need
to be solved.
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2. How can the problem be solved?
• Two of the methods used to answer
questions are descriptive research and
experimental research design.
• Descriptive research answers scientific
questions through observation.
• Experimental research design is used to
answer scientific questions by testing a
hypothesis through the use of a series of
carefully controlled steps.
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3. How can the problem be solved?
• Scientific methods
are ways, or steps to
follow, to try to
solve problems.
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4. Descriptive Research
• Some scientific problems can be solved, or
questions answered, by using descriptive
research.
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• Descriptive research is based mostly on
observations.
• Descriptive research can be used in
investigations when experiments would be
impossible to perform.
• Descriptive research usually involves the
following steps.

5. State the Research Objective
• This is the first step
in solving a problem
using descriptive
research.
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• A research objective is what you want to
find out, or what question you would like
to answer.

6. Describe the Research Design
• How will you carry out your investigation?
How will the data be recorded and analyzed?
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• An important part
of any research
design is safety. Click image to view movie.
• These are a few of the things scientists think
about when they
design an
investigation using
descriptive research.

7. Eliminate Bias
• Sometimes, scientists might expect certain
results. This is known as bias.
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• Good investigations avoid bias.
• One way to avoid bias is to use careful
numerical measurements for all data.
• Another type of bias can occur in surveys
or groups that are chosen for investigations.
• To get an accurate result, you need to use a
random sample.

8. Equipment, Materials, and Models
• When a scientific problem is solved by
descriptive research, the equipment and
materials used to carry out the investigation
and analyze the data are important.
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9. Using Models
• One part of carrying out the investigation
plan might include making or using scientific
models.
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• In science, a model represents things that
happen too slowly, too quickly, or are too
big or too small to observe directly.
• Models also are useful in situations in which
direct observation would be too dangerous or
expensive.

10. Using Models
• Dr. John Snow’s map of the cholera
epidemic was a model that allowed him to
predict possible sources of the epidemic.
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• Many kinds of models are made on
computers.
• Graphs, tables, and spreadsheets are models
that display information.

11. Scientific Methods
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• This allows them to
understand each
other’s research and
compare results.
• Scientists around the world use a system of
measurements called the International
System of Units, or SI,
to make observations.

12. Scientific Methods
• Because SI uses certain metric units that are
based on units of ten, multiplication and
division are easy to do.
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• Prefixes are used
with units to change
their names to larger
or smaller units.

13. Data—Designing Your Data Tables
• A well-planned investigation includes ways to
record results and observations accurately.
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• Data tables are one way to do this.

14. Analyze Your Data
• Your data must be organized to analyze them.
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• Charts and graphs are excellent ways to
organize data.
• You can draw the charts and graphs or use a
computer to make them.

15. Draw Conclusions
• After you have organized your data, you are
ready to draw a conclusion.
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• Sometimes, your data are not what you
expected, but remember, scientists understand
that it is important to know when something
doesn’t work.
• A successful investigation is not always the
one that comes out the way you originally
predicted.

16. Communicating Your Results
• Every investigation begins because a problem
needs to be solved.
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• Analyzing data and drawing conclusions are
the end of the investigation.
• Usually, scientists communicate their results
to other scientists, government agencies,
private industries, or the public.
• Scientists usually publish their most
important findings.

17. Communicating Your Results
• You can communicate your data and
conclusions to other members of your
science class.
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• Organized data and careful analysis will
enable you to answer most questions and
to discuss your work confidently.
• Analyzing and sharing data are important
parts of descriptive and experimental research.

18. Experimental Research Design
• Another way to solve scientific problems is
through experimentation.
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• Experimental research design answers
scientific questions by observation of a
controlled situation.
• Experimental
research design
includes several
steps.

19. Form a Hypothesis
• A hypothesis (hi PAH thuh sus) is a
prediction, or statement, that can be tested.
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• You use your prior knowledge, new
information, and any
previous observations
to form a hypothesis.

20. Variables
• In well-planned experiments, one factor, or
variable, is changed at a time.
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• This means that the variable is controlled.
• The variable that is changed is called the
independent variable.
• A dependant variable is the factor being
measured.

21. Variables
• To test which of two antibiotics will kill a
type of bacterium, you must make sure that
every variable remains the same but the type
of antibiotic.
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• The dependant variable is
the growth of the bacteria.
• In this experiment, the independent variable is
the amount or type of
antibiotic applied to the
bacteria.

22. Variables
• The variables that stay the same are called
constants.
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• You cannot run the experiments at two
different room temperatures, for different
lengths of time, or with different amounts
of antibiotics.

23. Identify Controls
• Your experiment
will not be valid
unless a control is
used.
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• A control is a sample that is treated like the
other experimental groups except that the
independent variable is not applied to it.

24. Identify Controls
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• In the experiment
with antibiotics,
your control is a
sample of bacteria
that is not treated
with either
antibiotic.
• The control shows how the bacteria grow
when left untreated by either antibiotic.

25. Identify Controls
• Once you begin an experiment, make sure
to carry it out as planned.
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• Don’t skip or change steps in the middle.
• Also, you should record your observations
and complete your data tables in a timely
manner.
• Incomplete observations and reports result
in data that are difficult to analyze and
threaten the accuracy of your conclusions.

26. Number of Trials
• Experiments done the same way do not
always have the same results.
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• To make sure that your results are valid,
you need to conduct several trials of your
experiment.
• Multiple trials mean that an unusual outcome
of the experiment won’t be considered the
true result.
• The more trials you do using the same
methods, the more likely it is that your
results will be reliable and repeatable.

27. Analyze Your Results
• When you analyze your results, you can see
if your data support your hypothesis.
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• If the data do not support your original
hypothesis, you can still learn from the
experiment.
• Experiments that don’t work out as you had
planned can still provide valuable information.
• Professional scientists rarely have results that
support their hypothesis without completing
numerous trials first.

28. Analyze Your Results
• After your results are analyzed, you can
communicate them to your teacher and
your class.
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• Sharing the results of experiments allows
you to hear new ideas from other students
that might improve your research.
• Your results might contain information that
will be helpful to other students.