PPDAC: A SCIENTIFIC
INQUIRY FRAMEWORK
Biol/Stat 2244 – Peter
Objectives
By the end of the course, you should be able to:
 name the five PPDAC stages and the questions
from the ‘Problem’ stage;
 describe the population of interest, sample, and
units for a study;
 use vocabulary associated with research (e.g.
variable, explanatory variable, parameter, etc.);
 classify the goal of a research study.
Biol/Stat 2244 – Peter
What is STATISTICS?
Biol/Stat 2244 – Peter
Scientific Inquiry Framework: PPDAC
(MacKay & Oldford, 2000)
Problem
Define the research question.
Plan
Decide how to address the research Problem.
Data
Execute your Plan and examine your Data.
Analysis
Extract meaning from your Data.
Conclusion
Interpret your results in the context of the Problem
Biol/Stat 2244 – Peter
Problem
A clear statement of what is to be learned, by
defining the research questions/objectives
• What is the population of interest? The units?
• What variables are under investigation?
• What parameter(s) is/are of interest?
• What is the goal of the research?
Biol/Stat 2244 – Peter
Problem – Example 1
Research Question:
Can outdoor cycling improve
cognitive functioning and wellbeing in seniors?
• Who/what are we focused on?
• What characteristics are we
interested in?
Images from Microsoft 365
Biol/Stat 2244 – Peter
All…..or some?
Population of interest:
complete collection of all
individuals/units to be
studied
Sample: subset of individuals/units from
whom/which data are collected
Why would we want or need to sample?
http://www.q4points.com/2012/03/stratified-sampling.html
Biol/Stat 2244 – Peter
Problem – Example 1
Research Question:
Can outdoor cycling improve
cognitive functioning and wellbeing in seniors?
• What is the explanatory
variable for this research
question?
Images from Microsoft 365
Biol/Stat 2244 – Peter
Variables
A characteristic that can take on different values
for different individuals/units.
Response variable measures an outcome of
interest in a study (also known as ‘dependent’)
Explanatory variable is thought to explain
differences or influence change in the response
variable (also known as ‘independent’)
Biol/Stat 2244 – Peter
Problem – Example 2
Research Question:
Does the type of material used in
playground surfacing influence
lead levels in Boston
playgrounds?
"Rubber EPDM Wet Pour Safety Surface Repair
suppliers.jpg;" by Soft Surfaces Ltd is licensed under
CC BY 2.0.
"Playground Primary Colors" by cwwycoff1 is licensed
under CC BY 2.0.
• What is the population of
interest?
• What variable(s) is/are
under investigation?
Biol/Stat 2244 – Peter
Parameter
A number that summarizes an attribute of a
population distribution
Example: Adults regularly biking
outdoors had a higher mean
improvement in Stroop test score
than non-cyclers.
Possible parameters (not an exhaustive list!):
• mean, median, mode
• variance, SD, range
• proportion, percentage • slope, intercept
• maximum, minimum
• others…
https://www.psytoolkit.org/lessons/stroop.html
Biol/Stat 2244 – Peter
Problem – Example 2
Research Question:
Does the type of material used in
playground surfacing influence
lead levels in Boston
playgrounds?
What are we trying to “do”
with this research?
"Rubber EPDM Wet Pour Safety Surface Repair
suppliers.jpg;" by Soft Surfaces Ltd is licensed under
CC BY 2.0.
"Playground Primary Colors" by cwwycoff1 is licensed
under CC BY 2.0.
Biol/Stat 2244 – Peter
Problem – Example 3
Research Question:
What percentage of
Canadian undergraduate
students participate in
academic misconduct?
What are we trying to “do” with this
research?
Image from Microsoft 365
Biol/Stat 2244 – Peter
Research Goal
Identifies the basic nature of the research
question(s)/objective(s)
• Descriptive – estimating the value of a
population parameter
• Causative – understanding how a change in
the value of an explanatory variable
influences the value of a response variable
• Predictive – predicting the value of a
variable for unit(s) in the population
Biol/Stat 2244 – Peter