# Experimental Design

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Experimental Design

## 1. Types of Experimental Designs:

### 1.1. Between Group Design

1.1.1. Making comparison between two groups or more.

1.1.1.1. 1- True Experiments

1.1.1.1.1. is the best approach to exploring the relationship between independent and dependent variables.offers the most control over variables. The main characteristic that all true experiments must have: *Random assignment of participants

1.1.1.2. 2- Quasi Experiments

1.1.1.2.1. involves selecting groups, upon which a variable is tested, without any random selection processes.

1.1.1.3. 3- Factorial Designs

1.1.1.3.1. A factorial experimental design is used to investigate the effect of two or more independent variables on one dependent variable.

1.1.2. It is the most common type of research, and it can take many forms:

### 1.2. Within-Group or Individual Designs

1.2.1. - limited number of participants - impossible to make more than 1 group

1.2.1.1. Time Series Design

1.2.1.1.1. - only a group of particpants - over aperiod of time - multiple pretest & posttest observations/measures

1.2.1.1.2. Variations

1.2.1.2. Repeated Measures Design

1.2.1.2.1. all participants in a single group participate in all experimental treatment

1.2.1.3. Single-Subject Designs

1.2.1.3.1. A/B Design

1.2.1.3.2. Multiple Baseline Design

1.2.1.3.3. Alternating Treatment Design

## 8. WHAT IS AN EXPERIMENT

### 8.1. A PRESCRIBED SET OF CONDITIONS

8.1.1. TEST -(IDEA,PRACTICE,PROCEDURE)

8.1.2. CHECK THE {INFLUENCE} ON OUTCOME/DV

8.1.3. DECIDE ON AN IDEA WITH WHICH TO 'EXPERIMENT'

8.1.5. DETERMINE PERFORMANCE ON OUTCOME

## 9. WHEN DO WE USE AN EXPERIMENT

### 9.1. INDEPENDENT VARIABLE

9.1.1. WHAT IS TESTED

9.1.2. WHAT IS MANIPULATED

9.1.3. THE ONLY CHANGABLE VARIABLE

9.1.4. INTENTIONALLY CHANGED BY THE EXPERIMENTER

9.1.5. FACTOR OR CONDITION MANIPULATED CAUSED CHANGE IN ANOTHER (BEHAVIOUR)OR(CONDITION)

9.1.6. CHANGE IT TO SEE THE CHANGES OF (DV,EFFECT,OUTCOME)

### 9.3. DEPENDENT VARIABLE

9.3.1. WHAT IS OBSERVED/MEASURED

9.3.2. WHAT IS AFFECTED BY IV

9.3.3. THE DATA COLLECTED DURING THE INVESTIGATION

9.3.4. RESULT OF THE MANIPULATION OF THE ID

9.3.5. STH MIGHT BE AFFECTED BY CHANGING THE IV VARIABLE

## 10. KEY CHARACTERISTISTICS OF EXPERIMENTS

### 10.1. RANDOM ASSIGNMENT

10.1.1. EQUATING THE GROUPS

10.1.1.1. INDIVIDUALS RANDOMLY ASSIGNED TO GROUPS

10.1.1.2. ANY VARIABILITY OF INDIVIDUALS EQUALLY DISTRIBUTE IN (GROUPS /CONDITIONS)

10.1.1.3. REDUCTION IN ERRORS

### 10.2. CONTROL OVER EXTRANEOUS VARIABLES

10.2.1. RANDOM ASSIGNMENT

10.2.1.1. CONTROL DECISION BEFORE EXPERIMENT

10.2.1.1.1. A DECISION MADE BEFORE THE EXPERIMENT

10.2.1.1.2. OCCURS ONLY IN EXPERIMENTAL SETTINGS

10.2.1.1.3. ASSIGNING INDIVIDUALS AT RANDOM INTO(EXPERIMENTAL GROUP/CONTROL GROUP)

10.2.1.1.4. EACH PARTICIPANT HAS EQUAL CHANCE OF BEING CHOSEN

10.2.1.1.5. UNBIAS AND FAIR

10.2.1.1.6. PROVIDING CONTROL FOR EXTRANEOUS VARIABLES

10.2.1.1.7. ITS EXPERIMENTAL TERM IS "EQUATING"

10.2.1.1.8. PARTICIPANTS ARE (AVAILABLE,VOLUNTEER)TO PARTICIPATE

10.2.1.2. THE MOST SOPHISTICATED TYPE OF EXPERIMENT INVOLVES RANDOM ASSIGNMENT

10.2.2. PRETESTS

10.2.2.1. PRETEST-POSTTEST DESIGN

10.2.2.1.1. PARTICIPANTS BEFORE

10.2.2.1.2. MANIPULATION

10.2.2.1.3. PARTICIPANTS AFTER

10.2.2.1.4. PARTICIPANTS MIGHT NOT RANDOMLY ASSIGNED(QUASI-EXPERIMENTAL)

10.2.2.1.5. POSSIBILITY OF HAVING CONTROL GROUP

10.2.2.1.6. THE REASON WE RUN THIS DESIGN IS TO SEE IF YOUR (MANIPULATION),HAS CAUSED A CHANGE IN THE PARTICIPANTS.

10.2.2.2.1. CAN EVALUATE ATTRITION/MORTALITY(DROPOUT FACTOR)

10.2.2.2.2. CAN BE USED TO SELECT PARTICIPANTS FOR THE EXPERIMENT

10.2.2.2.3. ASSESS EQUIVALENCY OF GROUPS WITH SMALL SAMPLE SIZE

10.2.2.3.1. TIME CONSUMING AND AWKWARD TO ADMINISTER

10.2.2.3.2. RAISE THE PARTICIPANTS' EXPECTATIONS ABOUT THE OUTCOME

10.2.2.3.3. DEMAND CHARACTERISTICS

10.2.2.3.4. REDUCES EXTERNAL VALIDITY

10.2.2.4. POSTTEST

10.2.2.4.1. MEASURING ATTRIBUTE/CHARACTERISTICS AFTER RECEIVING TREATMENT

10.2.2.4.2. IS GIVEN AFTER TREATMENT

10.2.2.4.3. OUTCOME

10.2.2.4.4. TESTING PARTICIPANTS AFTER DOING EXPERIMENT

10.2.2.5. PRETEST

10.2.2.5.1. PROVIDES A MEASURE ON ATTRIBUTE/CHARACTERISTICS BEFORE RECEIVING A TREATMENT

10.2.2.5.2. USED FOR EQUATING THE CHARACTERISTICS OF THE GROUPS

10.2.2.5.3. IS GIVEN TO EACH GROUP PRIOR TO INTRODUCTION

10.2.2.5.4. ASSURES THAT GROUPS ARE EQUIVALENT AT THE BEGINNING OF THE EXPERIMENT

10.2.2.5.5. IS GIVEN BEFORE MANIPULATION

10.2.3. COVARIATES

10.2.3.1. CONTROL PROCEDURES CAN BE USED BEFORE AND DURING THE EXPERIMENT

10.2.3.1.1. CONTROLLING EFFECTS OF PRETESTS ON DV

10.2.3.1.2. MEANS FOR EQUATING GROUPS

10.2.3.1.3. MEANS FOR CONTROLLING FOR POTENTIAL INFLUENCES THAT AFFECT DV

10.2.3.1.4. MAY EFFECT THE OUTCOME

10.2.3.1.5. ADDING TO A MODEL INCREASE THE ACCURACY OF THE RESULTS "PURE CAUSAL EFFECT"

10.2.3.1.6. CAN BE AN INDEPENDENT VARIABLE

10.2.3.1.7. NEED TO BE CONTROLLED

10.2.3.1.8. VARIABLES USING IN STATISTICS

10.2.4. MATCHING PARTICIPANTS

10.2.4.1. CONTROL PROCEDURES CAN BE USED BEFORE AND DURING THE EXPERIMENT

10.2.4.1.1. COMPLETELY RANDOMIZED DESIGN

10.2.4.1.2. RANDOMIZED BLOCK DESIGN

10.2.4.1.3. MATCHED PAIRS DESIGN

10.2.5. HOMOGENEOUS SAMPLES

10.2.5.1. CONTROL PROCEDURES CAN BE USED BEFORE AND DURING THE EXPERIMENT

10.2.6. BLOCKING VARIABLES

10.2.6.1. CONTROL PROCEDURES CAN BE USED BEFORE AND DURING THE EXPERIMENT

10.2.6.1.1. GENDER

### 10.3. MANIPULATION OF TREATMENT CONDITIONS

10.3.1. TREATMENT VARIABLES

10.3.1.1. MAJOR TYPES OF IV

10.3.1.1.1. TREATMENT

10.3.1.1.2. MEASURED

10.3.2. CONDITIONS

10.3.2.1. DIFFERENT LEVELS OF THE IV

10.3.2.1.1. A THREE-LEVEL TREATMENT VARIABLE

10.3.2.2. TREATMENT VARIABLES INCLUDE(CONDITIONS/LEVELS)

10.3.2.3. LEVELS ARE CATEGORIES OF A TREATMENT VARIABLE

10.3.2.3.1. CATEGORIES OF THE AMOUNT OF SLEEP HIGH MEDIUM LOW

10.3.3. INTERVENING IN THE TREATMENT CONDITIONS

### 10.4. THREATS TO VALIDITY

10.4.1. STATISTICAL CONCLUSION VALIDITY

10.4.2. CONSTRUCT VALIDITY

10.4.3. THREATS TO INTERNAL VALIDITY

10.4.3.1. HISTORY

10.4.3.1.1. THREATS RELATED TO PARTICIPANTS

10.4.3.2. MATURATION

10.4.3.2.1. THREATS RELATED TO PARTICIPANTS

10.4.3.3. REGRESSION

10.4.3.3.1. THREATS RELATED TO PARTICIPANTS

10.4.3.4. SELECTION

10.4.3.4.1. THREATS RELATED TO PARTICIPANTS

10.4.3.5. MORTALITY

10.4.3.5.1. THREATS RELATED TO PARTICIPANTS

10.4.3.6. INTERACTIONS WITH SELECTION

10.4.3.6.1. THREATS RELATED TO PARTICIPANTS

10.4.3.7. DIFFUSION OF TREATMENT

10.4.3.7.1. THREATS RELATED TO TREATMENT

10.4.3.8. COMPENSATORY EQUALIZATION

10.4.3.8.1. THREATS RELATED TO TREATMENT

10.4.3.9. COMPENSATORY RIVALRY

10.4.3.9.1. THREATS RELATED TO TREATMENT

10.4.3.10. RESENTFUL DEMORALIZATION

10.4.3.10.1. THREATS RELATED TO TREATMENT

10.4.3.11. TESTING

10.4.3.11.1. OCCUR DURING AN EXPERIMENT AND RELATE TO THE PROCEDURE OF THE STUDY

10.4.3.12. INSTRUMENTATION

10.4.3.12.1. OCCUR DURING AN EXPERIMENT AND RELATE TO THE PROCEDURE OF THE STUDY

### 10.5. OUTCOME MEASURE

10.5.1. THE EFFECT PREDICTED IN A HYPOTHESIS IN THE CAUSE-EFFECT EQUATION

10.5.2. ASSESSING INFLUENCE OF TREATMENT CONDITIONS ON (OUTCOME/DV)

10.5.3. SENSITIVE TO TREATMENTS IN THAT THEY RESPOND TO THE(SMALLEST AMOUNT OF INTERVENTION)

10.5.4. OUTCOME MEASURES NEED TO BE VALID DRAW VALID INFERENCES

10.5.4.1. DRAW VALID INFERENCES

### 10.6. THREATS TO EXTERNAL VALIDITY

10.6.1. INTERACTION OF SELECTION AND TREATMENT

10.6.1.1. MIXING AND COMBINING OF SEPARATE ELEMENTS

10.6.1.2. ALL SUBJECT FROM A DEFINED POPULATION RANDOMLY SELECTED

10.6.2. INTERACTION OF SETTING AND TREATMENT

10.6.3. INTERACTION OF HISTORY AND TREATMENT

### 10.7. GROUP COMPARISON

10.7.1. COMPARE SCORES FOR DIFFERENT TREATMENT ON AN OUTCOME

10.7.2. OFTEN IS THE FOCUS OF EXPERIMENTAL TREATMENT

10.7.3. GROUPS CAN BE COMPARED BETWEEN GROUPS/WITHIN GROUPS

10.7.3.1. CONTROL GROUPS

10.7.3.2. EXPERIMENTAL GROUP