Transcript environmental science

ENVIRONMENTAL SCIENCE
Chapter 2 Tools of Environmental
Science
2.2 Statistics and Models
2.2 Statistics and Models
Objectives
Explain how scientists use statistics.
Explain why the size of a statistical sample is
important.
Describe three types of models commonly
used by scientists.
Explain the relationship between probability
and risk.
Explain the importance of conceptual and
mathematical models.
Introduction
Most studies in environmental science
involve tremendous volumes of data
that need to be organized and
interpreted before they are useful.
Statistics is the collection and
classification of numerical data.
Statistics are widely used in many other
fields of study, such as sports.
How Scientists Use Statistics
Scientists use statistics for a variety of purposes
such as making comparisons, summarizations,
characterizations, and analyses.
A statistical population is a group of similar
things that a scientist is interested in learning
about.
Though a population may be made of similar
individuals, there are differences that can be
measured.
A mean is the number obtained taking the sum
of the data for a given characteristic and dividing
it by the number of individuals being measured.
How Scientists Use Statistics
The mean provides a single numerical
measurement for a given aspect of a
population.
Means of different populations can be
compared.
A distribution is the relative arrangement of
the members of a statistical population.
In a normal distribution, the data are grouped
symmetrically around the mean – forming a
bell-shaped curve.
How Scientists Use Statistics
Probability is the chance that something will happen.

For example, if you were to flip a coin, the probability that it
would land “heads-up” is 50%
A sample is the group of individuals or events selected to
represent the population.
Sample size is the number of objects or events sampled.

If you were to flip a coin 10 times, you sample size is 10 or
if you were to flip the coin 1000 times, the sample size is
1000
A sample size should be large enough to give an accurate
estimate for the whole population.
Statistics in Everyday Life
One common use of statistics in life is
weather forecasts that give “50% chance of
thundershowers this evening” on the news.
Statistics are also used when studying climate
change and atmospheric carbon dioxide.
Being able to recognize and understand
statistics allows one to be a better consumer
of information – especially information about
the environment on which we depend.
Statistics in Everyday Life
Risk is the
probability of an
undesirable
outcome.
Public perception of
risk can be much
different than risk
perception of
experts.
Models
Models are representations of objects or
systems.
Scientists use many different kinds of models
to learn about the natural world.
Physical models are three dimensional models
that one can touch


Physical models closely resemble the object or
system that they represent
A well known example of a physical model would
be a DNA molecule section showing the double
helix structure
Models
Graphical models include maps and charts.

Graphical models are good for showing
relationship between locations or routes
Conceptual models are verbal or graphical
explanations for how a system works or is
organized.


A conceptual model may be illustrated by a flow
chart
Scientists can create flow charts to understand
how a system fits together, components contained
in the system, relationship between components,
and cause and effect
Models
A mathematical model is one or more
equations that represents the way a system
or process works.

Like any model, mathematical models are only as
good as the data from which they were built
“garbage in, garbage out!”
Computer models are mathematical models
processed with computer technology and may
include massive amounts of data.
2
E = mc
Which is a Scientific Model?
References
Normal Distribution Test Results http://www.susd.org/district/assess/normaldis
t.cfm
Oil Risk (Figure 11) – Arms, Karen,
Environmental Science, Holt
DNA Model http://sbchem.sunysb.edu/msl/DNA.html
Alabama Geological Map http://geology.about.com/library/bl/maps/blala
bamamap.htm?terms=alabama+geology+map
Reference
Runway Model http://www.painetworks.com/pages/fr
/fr0227.html
Anatomical Model http://individual.utoronto.ca/twix/anat
omy/arguments.htm