Dr. Mazharul Islam 1

Dr. Mazharul Islam www.studyandjobs24.com 1

Email: [email protected]


Research Design A research design is the arrangement of conditions for

collection and analysis of data in a manner that aims to combine relevance to the research purpose with economy in procedure.

Properties or Characteristics of a Good Research Design In the view of various definition of research design, the

following characteristics are found.i) A good research design is an ethical research design;ii) A good research design is one that is capable of obtaining the

most reliable and valid data;iii) A good research design is one that is capable of measuring any

odd events in any circumstances;iv) A good research design is one that helps an investigator avoid

making mistaken conclusions;v) A good research design is one that can adequately control the

various threats of validity, both internal and external.

Need of Research Design: Research design is needed because it facilitates the smooth sailing of the various research operations, thereby making research as efficient as possible yielding maximal information with minimal expenditure of effort, time and money. Research design stands for advance planning of the method too be adopted for collecting the relevant data and the techniques to be used in their analysis, keeping in view the objective of the research and the availability of staff, time and money.


Different Types of research design: There are two types of research design such as 1. Experimental Research Design and 2. Non-experimental Research Design

1. Non-experimental Design: A non-experimental study is one in which the researcher just describes and analyze researchable problems without any manipulation of the situation.

2. Experimental Design: Experimental research design is an elegant way to find out how well a particular program achieves its goals. In which, the researcher manipulates the situation and measures the outcome of his manipulation.

Non-experimental DesignTypes of Non-experimental Design: There are three types of non-experimental design such as: I. Exploratory studies; II. Descriptive studies; and III. Causal studies.

I. Exploratory Studies: An exploratory study is a small scale study of relatively short duration which is undertaken when little is known about a situation or problem.Types of Exploratory Study: Exploratory study offers an opportunity to obtain insights into the problem through four categories such as i. Secondary Data Analysis; ii. Experience Survey; iii. Pilot Study; and iv. Case Study.

II. Descriptive Studies: Descriptive studies are those used to describe the

characteristics of a population or phenomena. The objective of the descriptive

study is to focus on “who”, “what’, “when” and “how” question.


Types of Descriptive Studies: There are seven types of descriptive studies such as i. Cross-sectional Study; ii. Longitudinal Study; iii. Trend Study; iv. Panel Study; v. Baseline Study; vi. Impact Assessment Study; and vii. Feasibility Study.

III.Causal studies: A casual also called explanatory or analytical study attempts to establish cause or risk factors for certain problems. Our concern in causal studies is to examine how one variable “affects “or is responsible for changes in another variable.

Types of Descriptive Studies: There are three types of causal studies such as i. Comparative Study; ii. Case-control Study; and iii. Cohort Study.


2. Experimental Design: Experimental research design is an elegant way to find out how well a particular program achieves its goals. In which, the researcher manipulates the situation and measures the outcome of his manipulation.

Characteristics of Experimental Design: The classical experimental study has three characteristics such as a) Manipulation; b) Control; and c) Randomization.a) Manipulation: Individuals, in an experimental study are

randomly selected and allocated to at least two groups. One group is subject to an intervention, often called experimental or test stimulus, while the other group(s) is not. In a true experimental study, the experimenter has the ability to measure the values of the dependent variable both before administering the stimulus and after administering it. The difference between these scores gives a rough indication of the effect of the causal variable.

b) Control: By control, we mean, all factors with the exception of the independent variable must be held constant and not confounded with another variable, that is not part of the study.

c) Randomization: By randomization, we mean that the researcher takes care to randomly assign subjects to the control and experimental groups, meaning that each subject is given an equal chance of being assigned to either group.


Advantages of Experimental Studies: A few advantages of an experimental study are following:i) If ensures researcher’s ability to manipulate the independent

or explanatory variable.ii) In experimental studies, contamination from extraneous

variables can be controlled more effectively than in other designs. This helps the researcher to isolate experimental variables and evaluate their impact over time.

iii) The cost and convenience of experimentation is much less compared to other methods.

iv) The experiment provides the opportunity for studying changes over time through repeated measurements. This replication leads to discovery of an average effect of the independent variable across people, situations and times.

v) The researchers can use naturally occurring events to reduce subjects’ perceptions of the researchers as a source of intervention or deviation in their everyday lives.

Disadvantages of Experimental Studies: A few disadvantages of an experimental study are following:i. Most social sciences research is conducted under artificial

environment. This is perhaps the main problem with using experimentation in social sciences where sufficient control is impossible in natural settings.


ii. The experiment can be a ‘reactive’ method in the sense that the experimenter’s expectation can affect the results of the experiment. Why does this happen? Perhaps one possible reason is that the experimenter gives cues (perhaps subconsciously) to the subjects, who then conform to the experimenter’s wishes.

iii.It is sometimes impossible to control all the extraneous variables.

iv.With large group of subjects, it is difficult to control over the environment. Thus the experiment is most widely used in psychological studies, where the focus of interest is generally one person at a time rather than a whole group.

v. Generalization from non-probability sample can pose problems despite random assignment.

vi.Despite low cost of experimental studies, many applications of experimentation outrun budgets.

vii.Experimentation is most effectively targeted at problems of the present of immediate future. Experimental studies of the past are not feasible and predictions are not possible in experimental studies.

viii.Intervention and control that are two important elements in experiments, is sometimes hard to achieve when ethical issues are involved.


Types of Experimental Design: There are three types of experimental design such as: I. Pre-Experimental Design; II. True-Experimental Design; III. Quasi-Experimental Design.

I. Pre-Experimental Design:Types of Pre-Experimental Design: There are three types of pre-experimental design such as i. Posttest-only Design; ii. Pretest-posttest Design; and iii. Static-group Comparison.

II. True-Experimental Design:A. Types of True-Experimental Design According to

Informal: i. Pretest-posttest Control Group Design; and ii. Posttest-only Control Group Design. There are two informal types of true-experimental design such as

B. Types of True-Experimental Design According to Formal: There are four formal types of true-experimental design such as i. Complete Randomized Design (CRD); ii. Randomized Block Design (RBD); iii. Latin Square Design (LSD); and iv. Factorial Design.

III. Quasi-Experimental Design: Types of Quasi-Experimental Design: There are four types of quasi-experimental design such as i. Non-equivalent Control Group Design; ii. Time-series Design; iii. Separate Sample Pretest-posttest Design; and iv. Ex-post Facto Design.

i. Non-equivalent Control Group Design: There are two types of non-equivalent control group design such as a) Intact Equivalent Design and b) Self-selected Experimental Design.


Completely Randomized DesignTo Set up a Completely Randomized Design (CRD) for 3 treatments T1,T2,T3 with 4 replications we have to consider the treatments as T1,T1,T1,T1,T2,T2,T2,T2, T3, T3,T3,T3.

Sl. No. 1 2 3 4, 5 6 7 8, 9 10 11 12

RN 29 31 72 34 52 03 08 13 35 26 90 9

Selected 5 7 12 10 4 3 8 1 11 2 6 9

Treat T2 T2 T3 T3 T1 T1 T2 T1 T3 T1 T2 T3

Yield or Outcome

Serial No. 1 2 3 4 5 6 7 8 9 10 11 12

Treatment T1 T1 T1 T1 T2 T2 T2 T2 T3 T3 T3 T3

Now we have to allocate these 12 treatments randomly in 12 plots using random numbers as follows:

T1 T2 T3 T4

y11 y21 y31 y41

y12 y22 y32 y42

y13 y23 y33 y43

y14 y24 y34 y44Notationyij= observation j in group I; i=1, 2, 3, . . . ,k=4 and j=1,2,3,…,ni ; N= Σni=16ӯi. = mean of data in group iyi.= total of data in group iӯ..= mean of all datay..= total of all data


The partitioning of sums of squares corresponds to partitioning of differences:Deviation of observation from overall mean= (deviation of observation from group mean) +

(deviation for group mean from overall mean) yij − ӯ..= (yij − ӯi. ) + (ӯi. − ӯ.. )

Sum square of deviation of observation from overall mean= (Sum square of deviation of observation from group mean) + (Sum square of deviation for group mean from overall

mean) Σ Σ(yij − ӯ..)2 = Σ Σ(yij − ӯi.)2 + Σ Σ(ӯi. − ӯ..)2

Σ Σyij 2- (y..

2 /N)= Σ Σ(yij − ӯi.)2 + Σ(yi.

2/ni) - (y..2 /N)

SS(Tot) = SS(Err) + SS(Tr)

Analysis of Variance (ANOVA)Table:Sources of Variation

Degree of Freedom

Sum Square

Mean Sum SquareCalculated F Tabulated F

Treatment k-1 SS(Tr) MSS(Tr)=SS(Tr)/(k-1)

F =MSS(Tr)/MSS(Err) F k-1;N-k;α =F0Error N-k SS(Err) MSS(Err) = SS(E)/(N-k)

Total N-1 SS(Tot)


35 35 35 40 41 39 45 46 47 50 51 52 0+ 0+ 0 + 0+ 1 +(-1) +(-1)+ 0+ 1 +(-1)+ 0+ 1=06

(-8) +(-8) +(-8) +(-3) + (-2)+(- 4)+2 + 3 + 4 + 7 + 8 + 9

(-8) +(- 3) + 3 +8

Mean,Ӯ..=516/12 =43

Mean,Ӯ1.=105/3 =35

Mean,Ӯ2.=120/3 =40

Mean,Ӯ3.=138/3 =46

Mean,Ӯ4.=153/3 =51


Randomized Block Design•Let us consider 5 Treatments: T1,T2,T3,T4 & T5 and No. of blocks: 4

Random selection of Treatments:

Block B1

R N Treat Block B2

R N Treat Block B3

R N Treat Block B4

R N Treat3 T3 6(1) T1 9(4) T4 2 T29(4) T4 2 T2 8(3) T3 5 T51 T1 5 T5 2 T2 8(3) T35 T5 8(3) T3 1 T1 9(4) T47(2) T2 4 T4 5 T5 1 T1

1 2 3 4 5B1 T3 T4 T1 T5 T2B2 T1 T2 T5 T3 T4B3 T4 T3 T2 T1 T5B4 T2 T5 T3 T4 T1

RANDOMIZED BLOCK DESIGN ( RBD)

T1 T2 T3 T4 T5

B1 y11 y12 y13 y14 y14

B2 y21 y22 y23 y24 Y25

B3 y31 y32 y33 y34 y35

B4 y41 y42 y43 y44 y45

Yield or Outcome Notationyij= observation of jth treatment and ith block; ӯi. = mean of ith block; yi.= total of ith blockӯ.j = mean of jth treatment; y.j= total of jth treatmentӯ..= mean of all datay..= total of all dataj=1, 2, 3, . . . ,k=5 and i=1,2,3,…,n=4 ; N= nk=20


Sum square of deviation of observation from overall mean= (Sum square of deviation for block mean from overall mean) + (Sum square of deviation for treatment mean from overall mean) + (Sum square of deviation of observation from block mean and treatment mean) Σ Σ(yij − ӯ..)2 = Σ Σ(ӯi. − ӯ..)2+Σ Σ(ӯ.j − ӯ..)2+ Σ Σ(yij − ӯi.- ӯ.j +ӯ..)2

Σ Σyij 2- (y..

2 /N)= Σ Σ(yij − ӯi.- ӯ.j +ӯ..)2 + Σ(yi.

2/k) - (y..2

/N) + Σ(y.j2/n) - (y..

2 /N)

SS(Tot) = SS(Err) + SS(blok) + SS(Tr)

Analysis of Variance (ANOVA)Table:

Sources of Variation

Degree of Freedom

Sum Square

Mean Sum SquareCalculated F Tabulated F

Treatment k-1 SS(Tr) MSS(Tr)=SS(Tr)/(k-1)F =MSS(Tr)/MSS(Err) F k-1;N-k;α =F0

Block n-1 SS(blok) MSS(blok)=SS(blok)/(n-1) F =MSS(blok)/MSS(Err)

F n-1;N-k;α =F0

Error N-k SS(Err) MSS(Err) = SS(E)/(N-k)

Total N-1 SS(Tot)


Latin Square Design• Latin Square With 5 treatments: T1, T2, T3, T4 & T5• i) Select a Stradard Latin Square.

• ii) Randomize the rows of selected Latin square.

• iii) Randomize colums of resultant Latin square except the first.

T3 T4 T5 T1 T2

T4 T5 T1 T2 T3T5 T1 T2 T3 T4

T1 T2 T3 T4 T5T2 T3 T4 T5 T1

T2 T3 T4 T5 T1T5 T1 T2 T3 T4T4 T5 T1 T2 T3T1 T2 T3 T4 T5T3 T4 T5 T1 T2

T2 T4 T1 T3 T5T5 T2 T4 T1 T3T4 T1 T3 T5 T2T1 T3 T5 T2 T4T3 T5 T2 T4 T1

RANDOM ROWS: R5, R3, R2, R4, R1

RANDOM ROWS: C1, C3, C5, C2, C4

Dr. Mazharul Islam 1

Documents

Transcript of Dr. Mazharul Islam 1