Research Design by Zennifer L. Oberio
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Transcript of Research Design by Zennifer L. Oberio
RESEARCH DESIGN
What is a research design?
A complete sequence of steps to be
followed for data-gathering
Provides structure to the research
Shows how all the major parts of the
research project work together to address
the research problem.
Good Research Design
A good research design …
Enhances the validity of the research
Minimizes the plausible alternative
explanations for the hypothesized cause-
effect relationship.
Considerations in Making the
Design
1. Objectives of the study/ Type of the study
2. Independent Variable / Manipulated variable
3. Dependent Variables/ Observation/ Measures
4. Treatment and Control
5. Subject of the study/ Test organisms
6. Samples or groups
7. Sampling plan
8. Method of assignment
9. Control of Extraneous Variables
10. Replicates/ Trials
11. Statistical Analysis
Definition of Terms
Independent Variable- manipulated,
measured, or selected by the researcher as
an antecedent condition to an observed
behavior;
(aka experimental, manipulated,
treatment, grouping)
Definition of Terms
Dependent Variable- factor which is
observed and measured to determine
the effect of the independent variable;
(aka outcome or responding)
Definition of Terms
Definition of Terms
Treatment- any procedure done on an
experimental unit
Control- a procedure carried out to give a
standard of comparison in an
experiment;
Definition of Terms
Definition of Terms
Subject- the main material used in the study
Test Organisms- organisms used for observation
of the effects of a certain treatment
Samples- subset of the population under
investigation that you select to be part of your
study
Groups- sets of members of the population that will
be assigned to treatments or controls
Definition of Terms
Definition of Terms
Random Assignment- every participant in
the experiment has an equal chance of being
assigned to any of the experimental or control
conditions being compared
Random Selection- every member of a
population has an equal chance of being
selected be a member of the sample.
Definition of Terms
Definition of Terms
Extraneous Variables- the parts of the
experiment that remain the same; factors
that must be kept constant in all experimental
runs
Replicates- the series of repetition of an
experiment or parts of an experiment to
secure more data to arrive at a smaller
standard errors
Definition of Terms
Definition of Terms
Trials- repeated observations or
measurement from the same sampling unit
Definition of Terms
Case 1: Pathogens in Street food
Jinky, Raff and Irene wanted to know if
E. coli is present in the juice sold in stalls in
front of three elementary schools in Iloilo
City. They chose the elementary schools
based on location and student population.
They took a survey of the stalls in front of
the school.
They randomly selected one stall per
school from which to buy the juice and
solicited the consent of the owners of the
chosen stalls. A certain volume of juice was
bought from each stall and was homogenized.
A sample was taken from the homogenized
juice and was used for the determination of
the presence or absence of the E. coli.
They prepared three petri plates for
each juice sample. These served as their
three trials for each juice sample. The
results were reported as the mean number
of colonies of E. coli observed in the juice
sample from the stall in each elementary
school.
Case SummaryCase 1: Pathogens in Street food 2. Independent Variable/ Manipulated variable :• None3. Dependent Variable/ Observations/ Measures: • Number of colonies observed4. Treatment and Control: • None5. Subject of the study/ Test organisms:• Subject : Fruit juice6. Samples or groups:• stalls , juice
7. Sampling plan:• Simple random sampling for
stall8. Method of assignment:• Haphazard to each plate
9. Control of Extraneous Variables: • Aseptic Techniques, culture
conditions (medium, temp, pH)
10. Replicates/ Trials:• 3 trials for each stall
11. Statistical Analysis:• Descriptive Statistics: mean no.
of colonies per stall
Case 2: Ultraviolet Light and Pechay
Keanne determine and compared the
amount of cellulose in the leaf, stem and
roots of pechay exposed to UV-B light for
three weeks at various lengths of exposure
period per day (0, 4, 6, 8, and 10 hours per
day). Keanne initially planted around 80
seeds
Out of the approximately 80 seedlings that
grew, she removed the very short and very tall
plants. Of the remaining seedlings, she randomly
selected 30 seedlings of approximately the same
sizes to be used in her experiment. Then she
prepared five boxes for each exposure period. She
randomly assigned 6 seedling to each of the five
boxes, each seedling serving as one replicate.
She exposed the plants in four boxes to
UV-B for 4, 6, 8, and 10 hours per day. One
box was not exposed to UVB. This served as
her control. As the plants grew, she made
sure that she applied the same care and
maintenance to the plants, such as
loosening the soil and weeding, in all boxes.
She also regularly made adjustment to the
height of the UV-B lamp to maintain a
distance of 75 cm to the top of the plants.
After three weeks, she harvested the pechay
plants. For each plant, she separated the
roots, stem and leaf and determined the %
cellulose of each part. She then compared
the cellulose content of each plant part
exposed to UV-B at varying durations using
Analysis of Variance and post-hoc analysis.
Case SummaryCase 2: Ultraviolet and Pechay
2. Independent Variable/Manipulated Variable:
• Duration of exposure to UV-B
3. Dependent Variable/Observations/
Measures:
• % cellulose measured
4. Treatment and Control:
• 0, 4, 6, 8, 10 hours of exposure per day
5. Subject of the study/Test organisms:
• Subject: Pechay
6. Samples or groups
• 1 group per treatment, 1
group for control, 6 sampling
units per group
7. Sampling plan• Simple random sampling for choosing 30 seedlings8. Method of assignment• Random assignment of seedlings to plant box9. Control of Extraneous Variables• soil, amount of water & fertilizer, cultural mgt practices10. Replicate/ Trials• 6 Replicates11. Statistical Analysis• Descriptive Statistics: mean % cellulose per plant part per exposure period Inferential Statistics: ANOVA of % cellulose per plant part
Case 3: Mangrove and
Mud crabs
Mark, Andy and Kate wanted to determine the
impact of mangrove reforestation on the
population of mud crabs. They chose two sites: a
mangrove area that was rehabilitated and a natural
mangrove forest. They selected two sites that are
similar in such characteristics as, the species of
mangroves in the area, the number of trees in the
area, water salinity and extend of tidal inundation.
They divide the sites into 20 areas and
randomly chose 5 areas where they laid 5
quadrats and counted the mudcrabs in each
quadrat during low tide. They gathered data
from the two sites on consecutive days. They
did this once a month for four months. Then
they computed for the population density in
each site for every month.
Using t-test, they compared the population
density between the reforested mangrove area and
the natural mangrove forest for four months.
Case SummaryCase 3: Mangroves and Mud crabs2. Independent Variable/ Manipulated Variable:• Presence and absence of reforestation(not manipulated)3. Dependent Variable/ Observation/ Measures:• Population density of mud crabs measured4. Treatment and Control:• None (existing sites were studied)5. Subject of the study. Test organisms:• Subject: Mud crabs6. Sample or groups 5 quadrats per site: each quadrat as a sampling unit
7. Sampling plan:• Location of quadrats were chosen by simple random sampling8. Method of assignment:• None needed9. Control of Extraneous Variables:• Criteria were set for selection of the two sites10. Replicates/ Trials:• 5 replicates per site11. Statistical Analysis:• Descriptive Statistics: mean population density Inferential Statistics: t-test to compare the population density in two sites
Case 4: Shells and
Flesh of Diwal
Sofia determined the relationship between shell length and flesh wet weight of diwal. She collected diwal from the seabedin Capiz. She instructed the diver to collect diwal with shells of different sizes. Out of the harvested shells, she selected 30 diwal of shell sizes ranging from the smallest to largest. For each diwal, she measured the shell length. She also dissected the diwal to remove its flesh, which she weighed. She recorded 30 pairs of data: the shell length paired to the flesh wet weight. She determined if a relationship existed between shell length and flesh wet weight by correlation.
Case SummaryCase 4: Shells and Flesh of Diwal2. Independent Variable/ Manipulated Variable3. Dependent Variable/ Observations/ Measures:• No dependent and independent variables: shell length and flesh wet weight were the two variables measured4. Treatment and Control:• None5. Subject of the study/ Test organisms:• Subject: Diwal6. Samples or groups:• 30 diwal; each diwal as a sampling unit
7. Sampling plan:• Purposive sampling of the 30 diwal8. Method of assignment:• None9. Control of Extraneous Variables:• None needed10. Replicates/ Trials:• None11. Statistical Analysis:• Inferential statistics: Correlation between shell length and flesh wet weight
Case 5: The Delivery
Robot
Mae Ann and Lynne designed and built a prototype of a robot that will deliver water at three predetermined times in one day at five stations within a space of predetermined lay-out. They determined the different component of the design: the mechanical parts and the computer program. They built a prototype robot, made the program and uploaded the program. Then, they conducted a performance evaluation of the robot by testing its capability in a simulated space. They conducted three evaluation runs.
CASE SUMMARY
2.Independent Variable/ Manipulated Variable:• None3.Dependent Variable/ Observations/ Measures:• None: The components of
the design that were reported and were evaluated as functioning or nonfunctioning as intended.
4.Treatment and Control: • None5.Subject of the study/ Test organisms:• Subject: Robot
6.Samples of groups:• None7.Sampling Plan:• None8.Method of Assignment:• None needed9.Control of Extraneous Variables:• None10.Replicates/ Trials:• None11.Statistical Analysis:• None
Case 5: The Delivery Robot
Dissecting the Cases…
OBJECTIVES/STUDY TYPE
Pathogen in Street food: DESCRIPTIVE
Ultraviolet and Pechay: EXPERIMENTAL
Mangrove and Mud crabs: QUASI-EXPERIMENTAL
Shell and Flesh of Diwal: CORRELATION
The Delivery Robot: DEVELOPMENTAL
Remember these…
Some Notes in Making the Design
• Objectives/ Type of the Study The type of research and the nature of the investigation dictates what research design to adopt in the study.
Tip: Check out the design of related studies in peer-reviewed research journals.
Some Notes in Making the Design
• Variables Identifying correctly the type of variables is important in choosing the appropriate statistics to use in reporting and analyzing your data.
Some Notes in Making the Design
• Replicates/ TrialsReplicates are a necessary element. The
experiment must be repeated enough number of times to give a sufficient estimate of variation among the observations within a group.
Three replications is the minimum. In experiments where death of organisms is a possibility, 5 or more replicates may be used.
Trials are made for measurements especially in descriptive studies where there are no replications.
Some Notes in Making the Design
• Statistical AnalysisThe number of groups, the variables, level of
measurement, the distribution of data, and your research objectives will determine the kind of analysis you will do.
Statistical TechniquesDescriptive
Central Tendencymean
median
mode
Variability Dispersionrange
Quartile deviation
SD variation
Shape/ dispersionsymmetry
skewness
Kurtosis
modality
Correlationbivariate
multivariate
regressionBivariate
Multivariate
InferentialHypothesis Testing
parametric
Non-Geometric
AssumptionPoint
Interval
Functions of Statistics: Description and Inference
Purpose
Inferential
Estimation Hypothesis
DECISION TREE FOR INFERENTIAL STATISTICS
Inferential
Estimation(quantitative)
Point estimate
Confidence interval
About x
Inferential
Hypothesis
Type of data
Type of data
Ranks
Two levels of independent
variables
Two levels of independent
variables
Type of data
Frequency countsGoodness of
fit
x2
Test of independence
x2
Means
1 independent variable
One sample
One sample 1
test
Two levels of independent
variables
independent
samples
Correlated samples
Two levels of independent
variables
Two independent variables
Independent samples
Factorial ANOVA
Independent t-test
Correlated t-test
Independent samples
Correlated samples
One-way ANOVA
TukeyHSD
TukeyHSD
Correlated measures ANOVA
Type of data
Type of data
Variances(parametric)
F-test
Some Notes in Making the Design
• Types of Design
Is random assignment used?
No
Yes
Randomized or true experiment
Is there a control group or multiple measures?
Yes No
Quasi-experiment non-experiment
Some Notes in Making the Design
• Basic Experimental DesignsCompletely Randomized Design(CRD)- Treatments are assigned randomly to the
experimental subjects without restrictions.
Randomized complete block design (RCBD)- Divides the experimental subjects into
more or less homogenous groups called blocks.
ReferencesAmamanglon KPH. 2007. The change in the cell wall components of the different parts of pechay (Brassica rapa) exposed to ultraviolet-B at varying duration[unpublished research paper]. Ilo-ilo City: Philippine Science High School Western Visayas 66p.
Araneta MEAM, Brasileo L.l. 2006. Line-follower robot: a technology to aid the elderly [unpublished research paper]. Iloilo City: Philippine Science High School Western Visayas 48p.
Billones I.R. Palma RMR, Villacastin AJB. 2006. Pathogenic bacteria found in various streetfood such as juices,food sauce and ready-to-eat fruits at randomly selected places in IloiloCity [unpublished research paper] Iloilo City: Philippine Science High School Western Visayas. 49p.
Cadornigara ML. 2012. Fundamentals of resarch, methods and models, Iloilo City: Mindset Publishin Inc.
Caintic HE, Cruz JM. 2008. Scientific research manual. Quezon City: C&E Publishing, Inc ,;147 p.
Contreras ST. 2008. Allometric models for diwal9Philas Orientalis) Iloilo City: Philippine Science High School Western Visayas
Parker SP, editor 1994. McGraw-Hill dictionary of scientific dictionary of scientific and technical terms fifth edition. New York: McGraw-Hill, Inc.; 2194p.
Adapted from: Zennifer L. Oberio PSHSWVAdapted by:Bacala, Kaitlyn MargarethOlivares, Jarred Sua-an, Zachary(Group IX)