Evaluating Theoretical Hypotheses
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Transcript Evaluating Theoretical Hypotheses
Scientific Inquiry
SCI 105
Evaluating Theoretical Hypotheses
Facets of Models
A model is
Abstract: details are intentionally omitted
Similar but not the same: to the real world
object that it represents
Part of the imaginary world
Its fitness to the (part of) real world needs to be
evaluated
It can be used to answer questions related to the
phenomena
Does it look
(physically) like
our campus?
Representations of Models
It’s crucial that a model can be presented
clearly and accurately, since it is
imaginary! (But it may be a fact if it’s right.)
Ways to present a (theoretical) model
Plain language: flexible, but lengthy and often
ambiguous
Visual symbols and diagrams: concise and
illustrative, but might not be accurate
Formal symbols and formulae: accurate, but
may be hard to convey the hidden meanings
Theoretical Models: A Simple Illustration
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DL
0
35
37 38
42
T(oC)
Heat transfer
Q
Q = c * (T - T0)
Linear expansion
DL = cl * (T - T0)
Theoretical Hypotheses
A theoretical hypothesis is to ask
Does the model fit the real world
In the intended aspects
To the intended degree of accuracy
Possible outcomes
True: fits as claimed
False: doesn’t fit
All scientific claims are hypotheses
The difference is in the fitness
A Model for Model Evaluation
Fit or not
Real World
Model
Observation/
Experimentation
Reasoning/
Calculation
Agree/Disagree
Data
Prediction
The Components
Real world: described in common language
Model : described in scientific terms
Hypothesis: specify the aspects and degree of accuracy
Data: expected results
All specific info that may be directly relevant
Obtained thru a process of physical interactions
Prediction: output from the model
Doesn’t need to be said ahead of time
A Six-Step Program
Real World
Identify a problem
No
Model doesn’t fit
Model
Describe it w/ sci.
terms
Prediction
Data agrees
prediction?
Data
Obtained by
observation or exp
Yes
No
Model does fit
D & P w/o
fitness?
Yes
Inconclusive
The Double Helix Case
RW problem: the DNA structure
Model: two-chain helical structure w/
bases mixed-paired in the center
Prediction: X(or diamond)-shaped pattern
in x-ray diffraction; A-T and
C-G ratios are 1:1
Data: Francis’s “B Form”; Chargaff’s
results; data that lead to Pauling’s
theories; and Avery’s results
Announcements
H/W Assignment
Ex 2.7: p 51-2 in Giere’s text
Identify the four components
Try to fit the episode into the 6-step program
Write a sentence/paragraph for each of comp/step
Submit a printed copy by Mon, at beginning of class