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Scientific Method
What is the Scientific Method?
• It’s a way to solve/explain a problem or
natural phenomenon, while removing
human bias and opinion. It is a critical
procedure that allows validity and
consistency in the science field.
The steps of the Scientific Method are:
• Observe & form a question
• Hypothesis
• Experimentation/collect & analyze data
• Conclusion/Share results/collaborate
Observe/Form a question
• What do we observe and How is a
question formed?
Prediction based on experience—
”if….then..”
Hypothesis
• Educated guess??
• It is a testable explanation.
• Hypothesis format in real world (applied
science) should be a statement that
answers a question to be investigated,
but does not follow the “if..then” format.
Write a hypothesis regarding the what
color of light (red, blue, or green) will help
a plant to grow the tallest.
One thing people usually associate science
with are experiments. But, even experiments
have very stringent (strict) requirements to
assure they are valid.
The key to good science experimentation is:
1. Make sure the experiment fits the
hypothesis.
2. That there is only one variable (independent variable )being tested.
3. That all other items in the experiment are
controlled. Includes Control group (group
not tested and used to compare results)
and constants.
4. All data is recorded, analyzed and
organized for accuracy and meaning.
5. The experiment (and results) are
repeatable.
Variables: A variable can be either dependent or independent.
Independent
• Affects the dependent
variable.
• The treatment--what
the experimenter is
doing or adding
• Graphed on the x axis
Dependent
• Is affected by the
independent variable
• The outcome, what is
being measured
• Graphed on the Y axis
Think back to your hypothesis
about plants and light color…
• Start by identifying variables, then
determine IV? And DV?
• In that scenario what would be a
control group?
• Constants?
A test for the effect of amount of light on plant growth is done so growth in mm is collected
every 2 days from plants both in the light directly and not in the light at all.
1) Identify the independent variable.
2) Identify the dependent variable.
3) Think of 3 constants that would be needed for an experiment like this.
4) What could your control group be? 5) Since this is the experiment, what steps occurred before this one?
Conclusion
• You will determine if the hypothesis was
supported or refuted.
• Give specific numerical/quantitative data
to support any claim that is made.
• Use reasoning to show
how your data is all
related and what trends
you can see.
2 Types of reasoning • 1- Inductive reasoning: broad predictions
based on one experience, witness or specific observations. (often based on trends). “Every time I’ve walked by that dog, he hasn’t tried to bite me. So, the next time I walk by that dog he won’t try to bite me.” “If” probably causes “then”. (not guaranteed correct outcome)
• 2- Deductive reasoning: Accurate/ guaranteed outcome based on logical and correct premise (When 99.9% of experiences and data lead to correct and consistent conclusion). “If”..always causes “then”.
Try these: A) Dinosaurs had feathers and the same anatomy
as modern birds. Dinosaurs are related to birds.
B) Water placed at different temperatures only
boils at 100 degrees Celsius.
C) Monocot flower parts are in multiples of three.
Apple flowers have five petals. Therefore, apple
trees are not monocots.
D) Your mom comes home every day at 3:00PM. So, when you hear the garage door at 3:03PM,
you know it is her.
Theory vs. Law • Organized system of accepted knowledge that explains a
phenomena
• Theory is a living document that explains why something
happens – (can be changed, but not discarded).
• Law explains how (often by using equations that can be
calculated and solved.
• Theory and law both represent the same level of certainty!!!
• Must be:
– Logical
– Peer reviewed
– Public
– Respectful of the
rules of evidence
*Check out this link (http://thehappyscientist.com/science-
experiment/gravity-theory-or-law )
Newton's first law of motion - an object in motion stays in motion with the
same speed and in the same direction unless acted upon by an
unbalanced force. (F=ma)
Pure Vs. Applied Science Pure
• Exact Science of
producing scientific
theories.
• There may be no
practical usage
• Doing science for the
sake of science
• Math and Theoretical
Physics
Applied
• Used to come up with
answers to problems
• Answers a question in
the natural world
• Driven by the need to
fix a problem or
change something
• Biology and Chemistry
Try These
• Development of String Theory
• Pharmaceutical research and drug testing
• Building different types of rocket engines in lab
• Using new rocket engines to travel farther into
space
Other factors that can influence
valid science: • Sample size
• Number of trials
• Lack of communication
• Opinions/bias (mistakes in measuring/recording data or ignoring data that doesn’t match expected results)
• Cultural differences
With a partner determine how each of these can influence valid science.
• In analyzing data while comparing the
relationship between our dependent
and independent variables, we can
determine the relationships that the
numbers (values) have. They will be…
Positive relationship (slope)
• Both X and Y values increase over
time.
Negative relationship (slope)
• One variable is increasing and the
other is decreasing.
Neutral relationship
• Y value stays constant over time.
Variables can be related • Causation: One variable causes the other to
change.
• Correlation: the variables both change but
due to an unknown outside factor.
Interpreting Data
Pre-Quiz:
Calculate the mean, median, mode, and range of the following numbers:
9, 8, 15, 8, 20
• Mean=
• Median=
• Mode=
• Range=
Mean=12 Median=9 Mode=8 Range=12
Interpreting Data
Mean (or average)
• The average is found by adding all the numbers together and then dividing them by the total of numbers that you added up.
• eg., 3, 4, 6, 5, 3, 5, 2 There are 7 numbers.
• 3 + 4 + 6 + 5 + 3 +5 + 2 = 28
• 28 ÷ 7 = 4 so the mean is 4
Interpreting Data
Median (or middle number)
The median is the middle number in a set of numbers. The median is found by lining all the numbers up in order and determining which number is in the middle. If the total number is odd then it is the actual center number.
If the total numbers are even find the two middle numbers, add them together and divide them by two. eg., 3, 4, 6, 5, 3, 4, 2
2, 3, 3, 4, 4, 5, 6 (line the numbers up)
The middle number is 4 so the median is 4.
Interpreting Data
Mode (or most common number)
The mode is the number that appears most often. The mode is found by lining all the numbers up and determining which number(s) occurs the most.
If none of the numbers are the same then the set of numbers has no mode.
eg., 3, 4, 6, 5, 3, 4, 2
2, 3, 3, 4, 4, 5, 6 (line the numbers up)
The 3 and 4 both occur twice so the mode is both 3 and 4.
Interpreting Data
Range
The range describes the ‘distance’ between the numbers. The range is found
by subtracting the smallest number from the largest number in the group.
eg., 3, 4, 6, 5, 3, 4, 2
The smallest number is 2. The largest number is 6. The range is from 2 - 6.
6 - 2 = 4 so the range of these numbers is 4
Watch these examples: Mean, median, mode
Interpreting Data
Practice:
Determine the mean, the median, the mode and the range of the following
sets of numbers.
1) 4, 5, 3, 3, 3, 2, 1
mean: _____________
median: _____________
mode: _____________
range: _____________
Graphing!!
• Once you have collected your data,
part of analyzing is often creating a
graph to you can notice trends,
relationships, and overall understand
what the data means.
• In science we will almost always use a
LINE GRAPH. Other types of graphs
can be effective but they are rare.
How to set up your graph
• IV is on the x axis and DV is on the Y axis.
• Numbers must be evenly distributed across the axis, do
not just copy your data table!
• Assume it is a line graph if there are numbers on both
axes or there is any measurement of time involved.
• You must always label both axis with numbers and units.
• You must always put a descriptive title on your graph.
• If there is more than one line, make a key.
• Your graph should take up all available space. Don’t
make a tiny graph in the corner of your graph paper!
LET’S GRAPH!!! Woohoo!!
LET’S GRAPH!!! Woohoo!!
Temperature (c)
Vo
lum
e (
mL)
LET’S GRAPH!!! Woohoo!!
Temperature (c)
Vo
lum
e (
mL)
The effect of temperature on volume of a liquid.