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)