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Experimental Design

Unit 1 - Science 7, Orion Jr. High, Utah

Cassie Grether

on 22 October 2015

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Transcript of Experimental Design

3. Mass/ Weight:
a) How to find mass:
place an object on a scale
1. scale:
digital scale or
triple beam balance
2. looks like:

b) measurements are in:
1. English:
pounds (lbs)
2. Metric:
grams (g) & kilograms (kg)
Experimental Design
Unit 1 - Science 7
I. Scientific Methods - many different ways for discovery, but they all use observation, logic, evidence, and analysis.
Jot this
chart down
Observation: the gaining of knowledge using the five senses (taste, touch, hear, feel, see)
Observation: the animal has feathers
NOT AN OBSERVATION: the animal flies
Experiment question: specific question that can be answered scientifically

Example: What are the effects of bleach on worms?
Non-example: How do the worms feel about bleach?
Vague question: What happens to worms affected by stuff?
Hypothesis: a prediction based on an observation and fact that can be tested
Testing and Observations
Once you have
gathered some
data, researched
your topic and come up with a hypothesis, it is time to test and make more observations.
But observation isn't always easy.
Analyze: to examine carefully and in detail for purposes of explanation and understanding

Evidence: observations, data, facts, measurements
Inference: your opinions or guesses that are based on the facts and evidence
Conclusion: what the data, inferences, and evidences mean to your hypothesis
II. Inference
How is an inference different than an observation, opinion, or fact?
An inference is what you can determine from the information, facts, and observations. You do this all of the time.

You smell cookies baking. What can you infer?
You hear rain pounding on the roof. What can you infer?
You feel the heat of a bedroom handle. What can you infer?
Difference between observation and inference
A boy comes in wearing a coat. He is holding an umbrella. His shoes are wet.
It is raining outside
What can we observe?
What can we infer?
So let's make a list.
II. Inference
A. How is an inference different than an observation?

III. What Makes a Good Experiment?
A. You must have a
testable hypothesis
. One that can be answered, and is specific.
Come up with an example:
B. Some experiments benefit from a
control group.
This is used to see if the test is normal or not.
Controls are used to compare your results to. This is what you keep the same and don’t change.
Underline this in your notes.
What were the controls in our gravity experiment?
If you have a highlighter pull it out now. If not, grab a light colored pencil.
Let's highlight or identify all the controls we used in our experiment.
C. Repeat experiments: The more data we have, the more
our results will be.
Even measurements can have issues: Each measurement could be slightly off, but if we can average all of our data or measurements, then we can have a better chance of accuracy with our results.
The Behavior of a Cheerleader
If we observe the how a cheerleader acts, just one, can we really get a good idea of how most behave?
What about our sports example? Can one person's opinion of their favorite sport really give us an idea of everyone's favorite?
With more information we can paint a more accurate picture of what is really going on.
Repeat experiments and repeated tests...
With more data you can be more accurate!
D1. We also need a
independent variable
. An
independent variable
is what you
. This is what you are testing.

Come up with an example:
Important Term
Independent variable: the variable that is changed or manipulated by the researcher
Let's highlight the independent variables in our gravity experiment.
Please insert this somewhere near dependent variable.
D2. While we are testing we will produce the dependent variable. That is the outcome of our test.
Important Term
Dependent variable: the response that we measure or the effects of our change that we made
Highlight time!
Let's find the dependent variable in our gravity experiment.
E. Then we run some sort of test. This will give us
to help support or not support our hypothesis. Evidence must be
and not an interpretation or inference.
F. During the entire experiment, the hardest thing is to stay impartial.
To be impartial means to try your best to be fair and not make early conclusions.
Don't let your bias or prior experience blind you to truth.
IV. Graphing (Which type of graph should I use and why?)
A. Line Graph
1. Looks like:

2. Why we use it:
used to track changes over time and/or distance.
3. Example: How fast a runner runs over time.
B. Pie Chart
1. Looks like:

2. Why we use it:
Parts of a whole - when you have 100 percent of something. They do not show change over time or distance.
3. Example: survey of people on their favorite sports team.
C. Bar graph
1. Looks like:

2. Why we use it:
Used to compare between different groups or different things.
D. X-Y Plot
1. Looks like:

2. Why we use it:
used to track changes over time and/or distance.
3. Example: How fast a runner runs over time.
V. Metric System
Way of measuring stuff where everything can be converted by some factor of 10!
Common Measuring Units
mass (weight): gram (g) & kilogram (kg)
volume (space): milliliter (mL) & liter (L)
distance: millimeter (mm), centimeter (cm), and meter (m).
100 centimeters = 1 meter
1000 millimeters = 1 meter

1000 milliliter = 1 liter
Do you see any similarities?
Converting between metric units is easier than English units. Let's try some conversions.
50 meters = ? centimeters
750 centimeters = ? meters
912 meters = ? centimeters
8,125 centimeters = ? meters
5,000 cm
7.50 m
91,200 cm
81.25 cm
VI. Measuring
A. Why we measure more than once?
1. All our measurements will be close, but not
perfect or exactly
the same. With more measurements and data we can make
averages (or means)
. This assures us that our results are more
2. Volume:
a measurement of space.
a) How you can find volume:
1. using math equations or
2. using a
graduated cylinder
(a) Looks like:

(b) measurements are in:
(1) English: cups
(2) Metric: liter
How to Measure Volume
the easy way...
5 mL
What is the name of the tube that measures volume?
graduated cylinder
17 mL
19 mL
2 mL
2 mL
What is the name of the tube that measures volume?
graduated cylinder
What is the name of the tube that measures volume?
graduated cylinder
What did we use to measure mass in our class?
triple beam balance
What did we use to measure mass in our class?
triple beam balance
What did we use to measure mass in our class?
triple beam balance
413.9 grams
80.6 grams
47.1 grams
moon walking bear
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