So now we are going to take our hypothesis
and dump it in and get something out of this.
Step 3 – we are going to test our hypothesis
and specifically we are going to test our
hypothesis by collecting objective data.
There are two different kinds of studies out
there when you look at ways to collect objective
data about a particular hypothesis.
Descriptive studies are going to record data
about variables in existing, natural systems.
So let’s say you want to find out who is
more susceptible to getting a cold than other
people.
You would go out and ask people about how
many hours of sleep they get and what they
eat and record whether they got colds or not.
That would be a descriptive study.
What you are going to do them is look for
relationships.
Is there some sort of relationship?
People who don’t sleep as much get more
colds...
So you are collecting data and looking for
relationships among those pieces of data.
An experimental study is when you manipulate
systems so that all variables are constant
except one.
So this is a much more manipulative system.
In this case, if we wanted to find out about
colds, maybe you would put everyone in a sleep
study and have everyone eat the same food
and have the same activity levels but have
one group get four hours of sleep and one
get group get eight hours of sleep and see
who comes down with a cold or not.
So we are keeping most of the variables constant
and manipulating just one part.
What this allows you to do in an experimental
study is figure out the effect of that one
variable.
We know whatever outcome we are seeing on
our dependent variable is due to this experimentally
manipulated independent variable.
So the question is – which of these is better?
Maybe in your brain right now you are answering
that – “oh I think descriptive studies”
or “oh I think experimental studies are
better.”
Of course, the answer is that it depends...
Over here, we have the descriptive study.
Descriptive studies are much easier to set
up.
Experimental studies are much more complex
to set up; there is a lot more work making
all the variables constant.
Because of this, descriptive studies are much
cheaper (generally) and experimental studies
are going to be much more expensive.
Descriptive studies actually describe the
real world, so you are going to go out and
get information about what is actually happening
in a human population with patients or in
an ecosystem, where in a lab setting, maybe
you are going to see what is happening rats
or with people in very artificial situations.
You are going to get some answers about a
variable but maybe not in real world situations.
The kicker here is that descriptive studies
give you correlations and experimental studies
can help establish cause and effect.
So what is the difference between these two?
A correlation is when two variables change
in some related way.
If one variable goes up, the other goes up.
Or if one variable goes up, the other goes
down.
This is some relationship – one variable
is changing in a way that is related to the
other.
That doesn’t always mean that one is causing
the other to change though.
A cause and effect relationship comes from
an experimental study and this is when we
know that one variable – in this case an
independent variable – is the reason why
the other variable is changing.
So let’s go ahead and look at some examples
of the difference between a correlation and
a cause and effect.
This video will show you some great examples
of that and issues that can come up when we
confuse the difference between a correlation
and a cause and effect.
