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.