Hi I'm Dr. Perkins and today
we're going to talk
about the Scientific Method.
The scientific method is a series of steps
that a scientist goes through
when carrying out an experiment.
It starts with observing
the world around us, and asking questions.
 
I observe this plant.
Observation is the first step in the scientific method
I notice that it grows
over time.
And I wonder
what conditions will make the plant grow better?
So, I develop a
hypothesis.
A hypothesis says that "If I do X,
then Y will happen."
A  hypothesis
is not just a guess. It's
an educated guess.  In my case, I read
about plants growing
better with Nitrogen.
My hypothesis is that if I add Nitrogen to the soil,
the plant will
grow faster. So
I add Nitrogen to this plant.
Nitrogen is called the treatment
but to know if Nitrogen had an effect on
plant growth, I have
to grow another plant without
Nitrogen. This plant is
the control. A
control represents a standard
for comparison. Both plants are
grown under exactly the same
conditions so that there is only
one variable: the Nitrogen.
The Nitrogen is called the
Independent Variable.  And
growth is called the
Dependent Variable.
It is the variable being
measured.  Then I collect data.
The data
represent my results.
I see the data.  I photograph my
data.  And...
here I'm displaying my data as
a line graph.  From
this data, I will draw a set
of conclusions. I conclude
that plants grow better in the presence of Nitrogen,
and notice that I have plotted
the dependent variable
on the Y-axis
and the independent variable
on the X-axis.
That is standard.  And so
from this graph you can see
the red line is plant
growing in the presence of Nitrogen
and the blue line is the plant
growing in the absence of Nitrogen.
So, I have a good conclusion. Is that a
good conclusion?  Well, sort of.
My experiment would have been strengthened if
I'd used a population of plants in
each group.  And that's
going to be my next experiment.
So, thank you for listening.
