Brain Teaser #1
Why
did the young
man name his
puppies Biology,
Chemistry and
Physics?
Brain Teaser #2
What
has a face
without eyes, and
hands without
arms?
Reasoning!? What’s that???
Reasoning is the act of drawing a conclusion.
 You use premises to help you draw a
conclusion. Some conclusions are more reliable
than others.
 It’s important to know if a conclusion was made
using deductive reasoning or inductive
reasoning. One is based on KNOWN FACTS
that can be proven. The other is based on
OBSERVATIONS that don’t always mean what
you think they do! Why is important to know
which one was used??

How do we start??

Reasoning starts by examining a premise, or
a statement.

After examining the premise, a conclusion is
made.
Deductive Reasoning

Deductive reasoning is the process of
reasoning from known facts to conclusions.
The known facts are trusted, or sound,
premises.

When you reason deductively, you can say
“therefore” with certainty.

If your facts are true to begin with, then your
conclusions will also be true.
Deductive Reasoning Example

Known Fact: The brochure for soccer camp
says cut-off date for camp registration is
June 6. All kids registering after that date will
go on a wait list, no exceptions.

Known Fact: It is three days past the cut-off
date, and you have not registered your child.

Conclusion: Your child will not be registered
and will go on the wait list.
Is the conclusion definitely true?
Partner A, tell partner B what you think the
answer is and why.
 YES!
 The argument starts with KNOWN FACTS!
 The conclusion is based on FACTS!
 If the cut off date is June 6 for registration,
and you are trying to register after June 6,
then you go on a waiting list! No exceptions!
 The conclusion can be made with certainty.
It is firm!

Will more evidence make your
argument stronger?
If you saw a website or got a phone call that
also said the deadline was June 6, would this
make your conclusion more convincing?
 Partner B, tell Partner A what you think the
answer is and why.


NO!

In deductive reasoning, once a solid statement
is made, you do not need more statements to
improve your conclusion.
Brain Teaser #3
What
did one half say
to the other half as
they were walking
down the road
together?
Deductive Reasoning

Does the argument start with a known
fact or an observation?

Is the conclusion definitely true?

Can you add more evidence to make it
more convincing?
Inductive Reasoning

Inductive reasoning is the process of going
from observations to conclusions. The
premise is something you have observed.

This type of conclusion is sometimes called
an inference.

Successful inductive reasoning depends on
the quality of your observations, or evidence.
Inductive Reasoning Example

Observation: Susan is seen walking from her
car to her home with a brand new tennis
racket.

Observation: Susan’s son, David, loves
tennis, and today is his birthday.

Conclusion (inference): Susan has bought
the tennis racket for David.
Is the conclusion definitely true?

Partner B, tell Partner A what you think the
answer is and why.

NO!
Susan could have borrowed a tennis racket
from someone.
 Susan could have bought herself a tennis
racket.
 The conclusion could be described as
probable, but not firm.

Will more evidence make your
argument stronger?
If you found a receipt for a tennis racket in
Susan’s car and a birthday card with a picture of
a tennis player on the front, would this make
your conclusion more convincing?
 Partner A, tell partner B what you think the
answer is and why.
 YES!
 In inductive reasoning, more evidence makes
your argument more convincing.

Brain Teaser #4
What
is it that leaves
but goes nowhere?
Inductive Reasoning

Does the argument start with a known
fact or an observation?

Is the conclusion definitely true?

Can you add more evidence to make it
more convincing?
Let’s take a moment to review…

What have we learned so far today?
 Reasoning is used to draw conclusions.
 There are two types, deductive and inductive.
 Deductive reasoning begins with known facts, the
conclusion is firm, and additional evidence does not
help make the conclusion more convincing.
 Inductive reasoning begins with observations, the
conclusion could be different than what we think, and
more evidence would help make the conclusion more
convincing.
Model – Deductive or Inductive
The National Heart Institute
researchers state that if you fry
food, you will add more fat than if
you had baked the food. The
choices in the cafeteria today are
fried chicken and baked chicken.
The fried chicken has more fat in
it than the baked chicken.
Model





Known fact: The National Heart Institute
researchers state that if you fry food, you will
add more fat than if you had baked the food.
Known fact: The choices in the cafeteria today
are fried chicken and baked chicken.
Conclusion: The fried chicken has more fat in it
than the baked chicken.
More evidence? Don’t need it! The researchers
are trusted experts. It’s a FACT, fried food has
more fat than baked food!
A different conclusion? No! There’s no way you
can be wrong if the known fact is correct!
Is this deductive or inductive
reasoning?
Questions to ask yourself:

Does the argument start with a known fact
or an observation?

Can you add more evidence to make it more
convincing?

Is there any other conclusion you could
make?
Whole Group – Deductive or Inductive?
Your teacher was sneezing
and blowing her nose a lot
today. You did not see your
teacher after lunchtime today,
and you noticed a substitute
teacher in her classroom.
Your teacher left early to go to
the doctor.
Whole Group – Deductive or Inductive?





Observation: Your teacher was sneezing and blowing
her nose a lot today.
Observation: You did not see your teacher after
lunchtime today.
Conclusion: She left early and went to the doctor.
More evidence? This would help confirm, or verify,
our conclusion! If we overheard her telling a
coworker that she was going to the doctor, our
conclusion would be more convincing!
A different conclusion? Of course! Our teacher could
be going to a meeting. That doesn’t mean she isn’t
sick, but we can’t say FOR SURE that she is going to
the doctor.
Partner – Deductive or Inductive?

You will be responsible for deciding whether
or not an example uses deductive or
inductive reasoning.

You must explain your decision to your
partner.

How will you decide which type of reasoning
was used to draw the conclusion?
Partner – Deductive or Inductive?

Partner A – Your best friend looked upset in
the hallway today. Lots of students were
holding Social Studies tests in their hands.
Your friend got a low score on the test.

Partner B – Students who receive more than
2 tickets are not allowed to go to incentive.
John has received 4 tickets this grading
period. He will not be at the incentive.
Partner B! Tell us what Partner A decided!
Your best friend looked upset in the hallway
today. Lots of students were holding Social
Studies tests in their hands. Your friend got a
low score on the test.
Known facts or observations? Observations
 Is the conclusion definitely true? NO!
 Would more evidence make the conclusion
more convincing? YES!
 What type of reasoning is this? INDUCTIVE!

Partner A! Tell us what Partner B decided!
Students who receive more than 2 tickets are
not allowed to go to incentive. John has
received 4 tickets this grading period. He will
not be at the incentive.
Known facts or observations? Known facts!
 Is the conclusion definitely true? YES!
 Would more evidence make the conclusion
more convincing? NO!
 What type of reasoning is this? DEDUCTIVE!

 Its
bottom is
hidden, its head
hard to find. Its
mouth always
open as it speaks
to mankind.
 Leaves no
footprints, nary a
track, travels the
world around and
back.
 No
light of its own, a
guide for men; mover
of waters Within a
sailors ken.
 A great transformer
but having no form;
useful at times, at
others, a storm.
 I exist at war’s outset,
in the midst of battle,
and at the end of all
conflict
Assessment
You will now test out your new skills by
completing an assessment.
 This assessment will let us know how well you
can use your new skills.
 Please do your best!
 Don’t forget to use your test taking skills.
 On the back of your paper, please complete the
So what? Who cares? What now? activity on
the next slide.

So What? Who cares? What now?









So what!?
What was our objective today?
What is deductive reasoning?
What is inductive reasoning?
Compare and contrast the two forms of reasoning. Use
a Venn diagram.
Who cares!?
How will learning this help you?
What now!?
What would happen to your deductive reasoning if the
premise that you started with was FALSE?!?