 
 
 
 
Hi. It's Paul Andersen and this
is Science and Engineering Practice 3, Planning
and Carrying Out Investigations. Investigations
are incredibly important in both science and
engineering. We use them in science to answer
questions that we hopefully have developed
on our own. And in engineering we use it to
test designs that we've created. And so investigations
are important but what comes out of an investigation
is going to be data. Data that we can then
analyze and use to reformulate new questions.
Or reformulate theories. And so when we're
thinking about carrying out investigations
the idea of a science lab and doing science
experiments brings up images like this. Of
a person working in a chemistry lab or physics
lab, gathering data, designing an experiment
and then they're testing out that experiment.
And that's a huge part of science and engineering.
But know this, there are a lot of science
that we do just through observations. And
so if you're studying ecology, this is an
ecological study using a quadrant right here,
you're going to do that by watching. Not designing
experiments but observing the earth and the
world and the way it works. And so astronomy
is going to be an observational science. Or
this right here is Jane Goodall working with
some students doing some ecological studies
or geology. We're getting out there and actually
making observations. It doesn't mean these
are not important. They're just as important
as the science investigations that we do.
They are a big part of science. And so not
all sciences is a scientific method of okay,
develop a hypothesis and go through that.
It's a big part of it but know that observational
science is also important. But when you're
planning an observation there are really three
steps you want to go through. Developing a
good question, coming up with the variables
and then coming up with the controls. And so let
me step you through that. Let's say I am observing
a pendulum. And I'm just watching a pendulum
swing back and forth and I'm trying to come
up with a good question. Now this is a virtual
pendulum so it will never stop. But a good
question that I might come up with is related
to the period. The period is how long it takes
for the pendulum to complete one cycle. So
from here (snap) (snap) so about 3 seconds
it sounds like. So it's about three seconds
to go through one period. And so maybe that's
going to be the factor that I want to study.
And so initially my question might be what
factors affect the period of a pendulum? We
then move on to the variables. And so what
could effect the period of a pendulum? And
I want to brainstorm as many ideas as I can
come up with. Maybe it's going to be the length
of the pendulum. How far it is from the pivot
point. Maybe the mass of the pendulum is going
to affect the period. It could be the amplitude,
in other words how far, what is the angle
away from just vertical. Maybe gravity is
going to affect it. Or air drag. Or there
could be a number of different things that
are going to affect it, but I want to come
up with one good one that I think I could
vary. And so let me choose, for example, shape
would be good as well. Let me choose amplitude.
And so I'm going to measure how the amplitude,
how high I release the pendulum is going to
affect the period. But I am going to hold
on to all these other variables and they'll
come in in just a second. And so basically
what I can do is I can now use those two variables,
amplitude and period, to come up with good
question or to refine my question. Because
in a good scientific investigation we really
only want to vary one thing and measure another.
And so I'm going to say amplitude and period
are going to be my variables. All those other
variables now become controls. Things that
I am going to have to keep the same in the
experiment. And so that it's going to have
to the same shape, it's going to have the
same amount of air. I would have a hard time
changing gravity, but it's going to have the
same gravity, mass, length. I really want
to come up with you know eight to ten things.
Maybe how I'm going to time it has to stay
the same. Or the way I release the pendulum
has to be the same. Or the pivot point and
what it is and how it's made has to be the
same. So I'm going to keep everything else
the same in my investigation except the thing
that I am going to vary, amplitude, and the
thing that I am going to measure. And that's
going to be the period. So you want to control
everything else in a scientific experiment.
If you don't, you're just going to get bad
data. Okay, once I've done that I'm going
to create a data table where I've got my amplitude
and my period. Now the amplitude is what we
call an independent variable. In an experiment
I am changing the amplitude, how high I drop
it from. And so that's going to be they independent
variable. The other variable then becomes
the dependent variable. So the period is going
to depend on the amplitude. And again, I vary
this one, and this one is going to be varied.
And in general, in science, we put amplitude,
or excuse me, the independent variable is
going to be in the first column and then the
dependent is going to be in the second. And
so let me start collecting some data. So now
we've got an amplitude of 135 degrees. I could
time it, so like that. And I could figure
out how long the period is. When I did this
earlier I found it was about 3.4 seconds.
How did I do that? Well the first time I started
doing it I simply started a stop watch and
timed how long it took to go back and forth.
But it seemed not very precise. And so what
I ended up doing was letting it swing back
and forth 10 times and I could get better
data. If we move to 120 degrees and I let
the pendulum swing that ends up with a period
that's going to be less. 3.1 seconds is what
I got. Or 90 degrees. It's going to be even
less. Okay, so what am I doing? I'm collecting
data now in my investigation. I can analyze
that, but we'll get to that in the next practice.
And so when you're carrying out investigations,
there's a few things that you definitely want
to talk about. One is accuracy and precision.
And so accuracy is how close am I to the right
answer? And so on this graph right here, if
this is the right answer, maybe the right
answer was for the first one was 3.3 seconds.
If I'm close to that then I am accurate or
my answer is close to the correct answer.
Precision looks at all the data that I collect.
In other words this is a good analogy. Let's
say I were to do that four times and I were
to get these values. Well they're going to
be pretty accurate. They're pretty close to
the right answer, but they're not precise.
And so if we were to look at this one, these
would be very precise answers. I do it over
and over and over again and I get answers
that are very close to each other, but they're
not close to the right answer. And so they're
not accurate. And so accuracy, are you correct,
precise is your data grouping together correctly.
And so it's really important that you repeat
the experiment over and over and over again
until you get data that's very very good,
accurate and precise. Because we want to be
right here in the middle of that target. Sample
size is very important then. Sample size is
how much data did you actually collect? If
you were to flip a coin and get heads would
you say every time I flip a coin I'm going
to get heads? Well, no. You know that you're going
to get tails some of the time. But if you
only do one trial, you're really doing that.
You're really just flipping the coin once
and so you want to flip the coin over and
over and over and over again. And so if I
were to do that pendulum experiment, don't
just do it once, but do it multiple times.
Get lots of data. Get an increased sample
size and you're going to get better data.
What is the goal then? Through our science
classrooms in relation to investigations you
want to be able to plan investigations, starting
with a good question and then controlling
your variables. Then you want to carry out
that investigation. Get good data and you
want to make sure you iterate that you do
it over and over and over again. And so let's
kind of talk about the progressions. So through
education, from elementary through high school,
how do you start by doing investigations and
then get better and better and better over
time? And so you start by starting with a
question. So you start with a good question.
You may want to give students quite a bit
of scaffolding. So in an elementary classroom,
a really good lab could be, let's let a ball
roll down a plane and then see what can we
do to change the speed? In other words if
we've changed the angle is that going to change
the speed? If we change the weight of the
ball? If we change the material that it's
made up of? So starting with a question that
you give your students is a good way to get
them headed in the right direction. As they
become older and older and older we want them
to start controlling more of the variables.
And so making sure that they're designing
the experiment. And so the best way to have
your students really understand, what a control
variable is, what an independent and what
a dependent variable do is to just have them
do it. And what they're going to find is that
in a lot of labs they're going to get bad
data. And you have to allow them to try it
again and again and again before they're going
to get better at designing. Next we want to
make sure that we're getting good data. Remember
in science we use that data to reformulate
theories again. And in engineering a good
way to make sure your students are getting
good data is through competition. So this
is like a Lego challenge right here where
robots are competing. In my own class we did
this Lego sumo competition. And it was a great
way to see how good your data fits against
other data by just competition through design.
And then finally we want to let students iterate.
You want to let them try to over and over
and over again. And scaffolding is a word
that works really well here. And so there
are just a few parts of good investigations.
And when students are younger, you want to
give them as much of that scaffolding as you
can. But as they get older and older and older
you want to kind of let them loose. Let them
do science on their own. It's sometimes a
little bit scary. It's going to take a little
bit more time to do investigations in your
class. But the students are going to learn
so much more if you can progress that way.
And I hope that was helpful.
