2.  Although scientists do not always follow a
rigid set of steps, investigations often follow
a general pattern. An organized set of
investigation procedures is called a scientific
method. Six common steps are found in
scientific methods shown in the next slides.
A scientist might add new steps, repeat
some steps many times, or skip steps all
together when doing an investigation.

3.  Many scientific investigations begin when someone observes an
event in nature and wonders why or how it occurs. Then the
question of “why” or “how” is the problem. Sometimes a
statement of a problem arises from an activity that is not
working. Some early work on guided missiles showed that the
instruments in the nose of the missiles did not always work. The
problem statement involved finding a material to protect the
instruments from the harsh conditions of flight.
 Later, NASA scientists made a similar problem statement. They
wanted to build a new vehicle—the space shuttle—that could
carry people to space and back again. Guided missiles did not
have this capability. NASA needed to find a material for the
outer skin of the space shuttle that could withstand the heat and
forces of reentry back into Earth’s atmosphere.

4.  Before testing a hypothesis, it is useful to learn
as much as possible about the background of
the problem. Have others found information
that will help determine what tests to do and
what tests will not be helpful? The NASA
scientists gathered information about melting
points and other properties of the various
materials that might be used. In many cases,
tests had to be performed to learn the
properties of new, recently created materials.

5.  A hypothesis is a possible explanation for a
problem using what you know and what you
observe . NASA scientists knew that a
ceramic coating had been found to solve the
guided missile problem. They hypothesized
that a ceramic material also might work on
the space shuttle.

6.  Some hypotheses can be tested by
making observations. Others can be
tested by building a model and relating
it to real-life situations. One common
way to test a hypothesis is to perform an
experiment. An experiment tests the
effect of one thing on another using
controlled conditions.

7.  Open another window and go to the
following website.
http://nces.ed.gov/nceskids/help/user_guide/
graph/variables.asp
 Use this website to define the following
terms.
› Independent variable
› Dependent variable

8.  Visit the websites below and read about
constants and the control group.
› http://www.monarchlab.org/mitc/Resources/StudentR
esearch/ScientificMethod.aspx
› http://www.ehow.com/info_8003575_constants-
controls-science-project-experiment.html
 After reading from both sites, write a definition
for the terms below.
› Constant
› Control (or control group)

9.  We will work on independent and dependent
variables, constants, and controls more
together in class!

10.  An important part of every experiment includes
recording observations and organizing the data into
easy-to-read tables and graphs. In the next couple
of days, you will learn about ways to display data.
 Interpreting the data and analyzing the
observations is an important step. If the data are
not organized in a logical manner, wrong
conclusions can be drawn. No matter how well a
scientist communicates and shares data, someone
else might not agree with the data. Scientists share
their data through reports, journals, and
conferences.

11.  Based on the analysis of your data, you decided
whether or not your hypothesis is supported.
When lives are at stake, such as with the space
shuttle, you must be very sure of your results.
For the hypothesis to be considered valid and
widely accepted, the experiment must result in
the same data every time it is repeated. If your
experiment does not support your hypothesis,
you must reconsider the hypothesis. Perhaps it
needs to be revised or your experiment needs
to be conducted differently.