Scientific Reasoning
Course
Forensic Science
Unit I
Safety &
Scientific Method
Essential
Question
How does
scientific
reasoning help in
our everyday
lives?
TEKS
§130.295(c)
(3)(A)(B)(C)
Prior Student
Learning
– Lab Safety
– Understanding
the Scientific
Method
Estimated Time
2 to 3 hours
Rationale
Scientific reasoning is a skill necessary to forensic science. Forensic
scientists need to be able to use scientific reasoning in order to process a
crime scene and the evidence found there.
Objectives
The student will be able to:
1. Analyze, evaluate, and critique scientific explanations by using data,
logical reasoning, and observations.
2. Communicate and apply scientific information from current events and
published articles.
3. Draw inferences based on data related to products and services.
Engage
Place several items in a bag that would describe a certain personality or
person. You might put things in that describe your being a teacher and what
hobbies you enjoy. Bring the bag to class, take out the objects, and show the
students. Have the students write down a personality profile of the person
who owns these belongings. Have them share with a partner and then select
some students to share with the class. Ask the students how they came up
with their profiles and then share the actual profile with the class. Use the
Discussion Rubric for assessment.
Key Points
I. Scientific Reasoning
A. The Cycle of Science
1. Scientific reasoning must use both inductive and deductive
reasoning
a) Inductive reasoning – moving from specific observations to
broader generalizations and theories
(1) Begin with specific observations and measurements, and
then detect patterns and regularities
(2) Formulate some tentative hypotheses that we can
explore
(3) Finally, develop some general conclusions or theories
b) Deductive reasoning – works from the general to the specific
(1) Begin with creating a theory about a topic of interest
(2) Narrow that down into a more specific hypothesis that we
can test
(3) Narrow that down even further when we collect
observations to address the hypothesis
(4) Test the hypothesis with specific data
B. How Scientists Reason
1. Scientists use analogies to form theories, generate hypotheses,
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C.
D.
E.
F.
and comprehend patterns of data
2. Scientists use the scientific method to generate these and create
experiments to test their hypotheses
Experimental Control
1. Scientists work to create experimental control
2. It is important for comparison so scientists know what has the
effect in an experiment
3. The control is the normal condition(s) for the subject being tested
Variable
1. The variable is the thing that is being changed in the experiment
2. You should only have one variable
Observation
1. Observations are recorded facts about what you see
2. There are two types of observations
a) Quantitative – results in a numerical form, with a unit
b) Qualitative – results in a descriptive form
Conclusions
1. Scientists make conclusions based on the data collected and the
observations made
2. Sometimes the conclusions prove the hypothesis and sometimes
they disprove the hypothesis
Activities
1. Lie Detector Article. Ask the question, “Are lie detectors reliable?” Students
will say yes or no. Have the students read an article about the newest
research in lie detection. (To find an article do an Internet search for the
following: Will Brain-Scanning Lie Detectors Free the Innocent or Jail
Them.) After the students have finished the reading, discuss the
information they learned from the article. Use the Discussion Rubric for
assessment.
2. Accuracy and Precision in the Food Industry. Have students analyze
various brands and types of lunch-sized bags of chips for accuracy and
precision of their printed weight on the bags. Then have students make
inferences based on their data (Note: Groups of 4–5 work best for this lab).
All of the students in a group need to bring the same brand, type, and size
of chip bag to class that day. Answers will vary based on the brand and the
type of chips. Assess the groups’ work for accuracy. Use the Individual
Work Rubric and the Group Evaluation for assessment as needed.
3. The Last Picnic. Students will use deductive reasoning to identify the
murderer in this activity. Use the Last Picnic handout for the activity. Use
the Last Picnic Key and the Writing Rubric for assessment.
Assessments
Scientific Reasoning Quiz and Key
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Last Picnic Key
Scientific Method and Reasoning Worksheet Key
Discussion Rubric
Individual Work Rubric
Group Evaluation
Writing Rubric
Materials
Scientific Reasoning computer-based presentation
Computer with Internet access
Last Picnic Handout and Key
Scientific Method and Reasoning Worksheet and Key
Accuracy and Precision Lab
– Accuracy and Precision in the Food Industry Lab Handout
– Bags of chips
– Scales
– Marking pen
Resources
Davis, Raymond. Modern Chemistry. Holt McDougal; 1st Edition, 2002
Francisco Redi Experiment http://www.scientus.org/Redi-Galileo.html
Do an Internet search for the following:
 Will Brain-Scanning Lie Detectors Free the Innocent or Jail Them
 Burgled Bonuses
Accommodations for Learning Differences
For reinforcement, students will complete the Scientific Method and
Reasoning Worksheet. Use the Scientific Method and Reasoning Worksheet
Key for assessment.
For enrichment, students will solve an educational game. (To find a game do
an Internet search for the following: Burgled Bonuses.) Use the Individual
Work Rubric for assessment.
State Education Standards
Texas Essential Knowledge and Skills for Career and Technical Education
§130.295. Forensic Science (One Credit).
(3)
The student uses critical thinking, scientific reasoning, and
problem solving to make informed decisions within and outside
the classroom. The student is expected to:
(A)
in all fields of science, analyze, evaluate, and critique
scientific explanations by using empirical evidence,
logical reasoning, and experimental and observational
testing, including examining all sides of scientific
evidence of those scientific explanations, so as to
encourage critical thinking by the student;
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(B)
(C)
communicate and apply scientific information extracted
from various sources such as current events, news
reports, published journal articles, and marketing
materials;
draw inferences based on data related to promotional
materials for products and services;
College and Career Readiness Standards
I. Nature of Science: Scientific Ways of Learning and Thinking
B. Scientific inquiry
1. Design and conduct scientific investigations in which hypotheses are
formulated and tested.
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Name:___________________________Date:____________________________
Scientific Reasoning Quiz
1) ____What type of reasoning do scientists use when looking at problems?
a. Inductive
b. Deductive
c. Inductive and deductive
d. Operational
2) ____What type of reasoning moves from specific observations to general theories?
a. Inductive
b. Deductive
c. Scientific
d. Operational
3) ____What type of reasoning moves from general to specific?
a. Inductive
b. Deductive
c. Scientific
d. Operational
4) ____Why is it important for an experiment to contain a control?
a. So that scientists can take measurements
b. So that scientists can compare what has the effect in the experiment
c. So that scientists can make observations
d. So that scientists can hypothesize
5) ____What is the condition being changed in an experiment called?
a. Control
b. Observation
c. Variable
d. Changer
6) ____Observations that are in numeric form are called_______.
a. Qualitative
b. Quantitative
c. Control
d. Variable
7) ____Observations that are in descriptive form are called_______.
a. Qualitative
b. Quantitative
c. Control
d. Variable
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8) ____Scientists use observations in order to formulate __________.
a. Conclusion
b. Control
c. Hypothesis
d. Variable
9) ____Which of the following would be considered a qualitative observation?
a. 10 ft long
b. 3.9 meters wide
c. 10º C
d. Bright purple
10) ____Which of the following would be considered a quantitative observation?
a. 3.5 meters
b. Bubbles vigorously
c. Reacts with acid
d. Forms a blue precipitate
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Scientific Reasoning Quiz Key
1) C
2) A
3) B
4) B
5) C
6) B
7) A
8) C
9) D
10) A
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Name:_____________________________________ Date:____________________________
Accuracy and Precision in the Food Industry
Objective: Students will analyze lunch-sized bags of chips to determine the accuracy and
precision of the food industry.
Procedure:
– In this lab, define accuracy as the net weight  0.10 grams
– Define precision as having a variance  0.20 grams
– All measurements need to be to two decimal places and must include units
– Each student in the group should have the same type of chip and same size bag to
proceed
Step 1: Label your bag of chips with numbers before you start to weigh them.
Step 2: Weigh each unopened bag individually. This is the gross weight.
Step 3: Open each bag and dump the contents onto a paper towel. Weigh each empty
bag individually. This is the tare weight. You may eat the contents.
Step 4: Calculate the net weight for each bag by subtracting the tare weight from the
gross weight.
Step 5: Determine if each bag's content is accurate. Prove your answer on the next
page.
Step 6: Determine if all of the bags together are precise. Prove your answer on the next
page.
Step 7: What inferences can be made about the manufacturer and the accuracy of their
products’ weight?
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Data Table:
Type of Chips: __________________________________________________
The NET WEIGHT (in grams) printed on the bag of chips: __________________
Bag #
Gross Weight
Tare Weight
Net Weight
1
2
3
4
5
Determine if the bags are precise.
Largest net weight =
__________________
Smallest net weight =
__________________
Variance =
__________________
Do you consider the weights on the bags of chips to be precise? Why?
Prove if each bag is or is not accurate.
Bag 1
Bag 2
Bag 3
Bag 4
Bag 5
Net Weight
Bag's
Printed Net
Weight
Variance
Accurate?
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Name:_____________________________________ Date:____________________________
The Last Picnic
Objective: Use deductive reasoning to decide who committed the murder.
Background:
Carrollton police discovered the body of a 26-year-old white male (later identified as Matt
Thomas) in an open field of sunflowers about five miles outside of downtown Carrollton. Mr.
Thomas’ body was discovered at 10:32pm Friday night, September 5th. He was found lying faceup on a yellow twin sheet. According to the coroner’s report, one fatal gunshot to the back of the
head ended his life. Scientists estimate that death occurred about 7:45pm. The following notes
were taken by the investigators at the scene:
 Paper plates with partially eaten sandwiches, chips, and chocolate cake were located
near the body
 A bottle of white wine and two partially filled glasses of wine were found next to the
yellow sheet
 One of the glasses had a smudge of pink lipstick on the rim
 Footprints from the road to the field were those of a male, size 11 and a female, size 6.
The only footprints from the field back to the road were those of a female, size 6
 Car tracks of the same wheel base and tread as those on Mr. Thomas’ automobile were
found at the road. The car was not found at the scene
 Later that same night Mr. Thomas’ car was found abandoned in a parking lot in
downtown Carrollton
Investigators believe that a female friend of Matt Thomas was responsible for his death. After
questioning family and friends, it was discovered that the deceased had frequent social outings
with six women who live in or near Carrollton. The women’s names are Anna, Evelyn,
Stephanie, Kaitlyn, Alexa, and Sabrina.
In this activity you will answer these questions: Who was responsible for the murder? What
events surrounded the murder?
Procedure:
1. After reading the background information, record some important pieces of information in
Data Table 1
2. Read the special notes below that the police gathered during their investigation:
 Kaitlyn works full time as a cosmetologist
 Alexa and Stephanie are school teachers
 Sabrina and Alexa live together in a two-bedroom apartment downtown
 Stephanie lives in a nearby town called Lewisville
 Anna lives in the country, about 10 miles west of Carrollton
 Alexa and Kaitlyn are very petite women – they wear size 4 jeans
 Kaitlyn works part-time as a fitness instructor at a health club in Carrollton. She
teaches a 7:30pm class each Friday night and has not missed a class in two years
 Sabrina is deathly allergic to grapes
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









Sabrina does not wear lipstick
Stephanie attends the fitness class that Kaitlyn teaches. She has not missed a
Friday night in 9 months
Evelyn works at a chemical supply store
Anna is allergic to all flowering plants
Anna’s father owns a shooting range
Anna is a florist
Anna doesn’t wear lipstick
Kaitlyn and Alexa have never met
Kaitlyn and Stephanie hate the color yellow
Evelyn played center for a semiprofessional basketball team five years ago. She
has red hair and is 6 feet, 1 inch tall
Questions:
1) Who do you believe killed Mr. Thomas?
2) What important information caused you to believe the other five women were innocent?
3) What information helped you identify the murderer?
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4) Write a two paragraph story that describes what you believe happened on the night of the
murder. Explain how the couple got to the field, why they went, what happened while they
were there, and how the murderer escaped. What was her motive?
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Data Table 1:
Question
Answer
Description and location of where the body
was found
Approximate time and day of death
Weapon used to inflict the fatal wound
Description of evidence impressions at the
crime scene
Description of objects found at the crime
scene
Any other evidence that may help solve
the crime
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The Last Picnic Key
1)
2)
3)
4)
Alexa
Answers may vary
She lives downtown and has small feet
Stories will vary. Use the Writing Rubric to assess this question.
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Name:_____________________________________ Date:____________________________
Scientific Method and Reasoning Worksheet
Long ago, many people believed that living things could come from nonliving things. They
thought worms came from wood and maggots came from decaying meat. This idea was called
spontaneous generation. In 1668, an Italian biologist, Francesco Redi, performed experiments
to prove that maggots did not come from meat. One of his experiments is shown below.
Redi placed pieces of meat in several jars. He divided the jars into two groups. He covered the
first group of jars with fine cloth. He left the second group of jars uncovered. Redi observed the
jars for several days. He saw flies on the cloth of the covered jars, and he saw flies laying eggs
on the meat in the uncovered jars. Maggots appeared only on the meat in the group of jars left
uncovered.
1. Scientists use a series of organized steps called scientific method to solve problems. List the
steps of the scientific method.
2. What was the problem in Redi’s experiment ?
3. What do you think his hypothesis was?
4. How did he test his hypothesis?
5. What was the variable in his experiment?
6. What was the control in his experiment?
7. What do you think Redi’s conclusion was?
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Scientific Method and Reasoning Worksheet Key
1) State the Problem, Research the Problem, State the Hypothesis, Design an Experiment,
Collect Data and Observations, Conclusion
2) Do maggots come from rotten meat?
3) Answers will vary
4) Placed meat in glass jars. Some open to the air. Some covered with cloth. He made
observations over several days
5) Covered jars
6) Open jars
7) Flies land on the uncovered meat and lay eggs which hatch and become maggots
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Name_______________________________
Date________________
Group Evaluation
Group 1
Did the group take the assignment seriously?
No
1
2
3
4
5
6
7
8
9
Yes
10
Could you tell what the group was trying to portray?
No
1
2
3
4
5
6
7
8
9
Yes
10
Was the group portrayal creative?
No
1
2
3
4
5
6
9
Yes
10
9
Yes
10
7
Did the group include the correct elements?
No
1
2
3
4
5
6
7
8
8
Would you like to see this group demonstrate their talent for you in the future?
No
Yes
1
2
3
4
5
6
7
8
9
10
Total Score_______
Group 2
Did the group take the assignment seriously?
No
1
2
3
4
5
6
7
8
Could you tell what the group was trying to portray?
No
1
2
3
4
5
6
7
8
Was the group portrayal creative?
No
1
2
3
4
5
6
7
Did the group include the correct elements?
No
1
2
3
4
5
6
7
8
8
9
Yes
10
9
Yes
10
9
Yes
10
9
Yes
10
Would you like to see this group demonstrate their talent for you in the future?
No
Yes
1
2
3
4
5
6
7
8
9
10
Total Score_______
17
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Group 3
Did the group take the assignment seriously?
No
1
2
3
4
5
6
7
9
Yes
10
Could you tell what the group was trying to portray?
No
1
2
3
4
5
6
7
8
9
Yes
10
Was the group portrayal creative?
No
1
2
3
4
5
6
8
9
Yes
10
8
9
Yes
10
7
Did the group include the correct elements?
No
1
2
3
4
5
6
7
8
Would you like to see this group demonstrate their talent for you in the future?
No
Yes
1
2
3
4
5
6
7
8
9
10
Total Score_______
Group 4
Did the group take the assignment seriously?
No
1
2
3
4
5
6
7
9
Yes
10
Could you tell what the group was trying to portray?
No
1
2
3
4
5
6
7
8
9
Yes
10
Was the group portrayal creative?
No
1
2
3
4
5
6
8
9
Yes
10
8
9
Yes
10
7
Did the group include the correct elements?
No
1
2
3
4
5
6
7
8
Would you like to see this group demonstrate their talent for you in the future?
No
Yes
1
2
3
4
5
6
7
8
9
10
Total Score_______
18
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Group 5
Did the group take the assignment seriously?
No
1
2
3
4
5
6
7
9
Yes
10
Could you tell what the group was trying to portray?
No
1
2
3
4
5
6
7
8
9
Yes
10
Was the group portrayal creative?
No
1
2
3
4
5
6
8
9
Yes
10
8
9
Yes
10
7
Did the group include the correct elements?
No
1
2
3
4
5
6
7
8
Would you like to see this group demonstrate their talent for you in the future?
No
Yes
1
2
3
4
5
6
7
8
9
10
Total Score_______
Group 6
Did the group take the assignment seriously?
No
1
2
3
4
5
6
7
9
Yes
10
Could you tell what the group was trying to portray?
No
1
2
3
4
5
6
7
8
9
Yes
10
Was the group portrayal creative?
No
1
2
3
4
5
6
8
9
Yes
10
8
9
Yes
10
7
Did the group include the correct elements?
No
1
2
3
4
5
6
7
8
Would you like to see this group demonstrate their talent for you in the future?
No
Yes
1
2
3
4
5
6
7
8
9
10
Total Score_______
19
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Name_______________________________________
Date_______________________________
Discussion Rubric
Objectives
4 pts.
Excellent
3 pts.
Good
2 pts. Needs Some
Improvement
1 pt. Needs Much
Improvement
N/A
Pts.
Participates in group discussion
Encourages others to join the
conversation
Keeps the discussion progressing
to achieve goals
Shares thoughts actively while
offering helpful recommendations to
others
Gives credit to others for their ideas
Respects the opinions of others
Involves others by asking questions
or requesting input
Expresses thoughts and ideas
clearly and effectively
Total Points (32 pts.)
Comments:
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Name______________________________________
Date_______________________________________
Individual Work Rubric
4 pts.
Excellent
Objectives
3 pts.
Good
2 pts. Needs Some
Improvement
1 pt. Needs Much
Improvement
N/A
Pts.
Follows directions
Student completed the work as directed,
following the directions given, in order and to the
level of quality indicated
Time management
Student used time wisely and remained on task
100% of the time
Organization
Student kept notes and materials in a neat,
legible, and organized manner. Information was
readily retrieved
Evidence of learning
Student documented information in his or her
own words and can accurately answer questions
related to the information retrieved
*Research/Gathering information (if relevant)
Student used a variety of methods and sources
to gather information. Student took notes while
gathering information
Total Points (20 pts.)
Comments:
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Name:____________________________________
Date:_____________________________
Writing Rubric
4 pts.
Excellent
Objectives
3 pts.
Good
2 pts. Needs Some
Improvement
1 pt. Needs Much
Improvement
N/A
Pts.
The writing has all required parts from
introduction to conclusion in smooth
transition.
The writing is interesting, supportive,
and complete.
The writing demonstrates that the
writer comprehends the writing
process.
Accurate spelling, grammar, and
punctuation
The content of paragraphs
emphasizes appropriate points.
The writer shows an understanding of
sentence structure, paragraphing, and
punctuation.
All sources and references are clearly
and accurately documented.
Total Points (28 pts.)
Comments:
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