RESEARCH (CORRELATIONAL)

EXPERIMENTAL RESEARCH

Enables the researcher to determine whether the treatment has had an effect or whether one treatment is more effective than another.

• The One-Shot Case Study

- A single group is exposed to a treatment and its effects are assessed • A single measure is recorded after the treatment in administered. • Study lacks any comparison or control of extraneous influences. • To remedy this design, a comparison could be made with another group.

• The randomized Posttest-only Control Group Design

- Both groups receiving different treatments

Multiple Regression

- Is a technique that enables to determine a correlation between a criterion variable and the best combination of two or more predictor variables.

• The Randomized Pretest-Posttest Control Group Design

- Pretest is included in the design

The One-Group-Pretest-Posttest Design

- Single group is measured both before and after a treatment exposure • Subjects are measured before and after treatment is administered. • Uncontrolled-for threats to internal validity exist. • To remedy this design, a comparison group could be added.

• The Static-Group Comparison Design

- Two intact groups receive two different treatments • Use of 2 existing, or intact groups. • Experimental group is measured after being exposed to treatment. • Control group is measured without having been exposed to the treatment.

1. Only type of research that attempts to influence a particular. 2. Best type of research for testing hypotheses about cause and effect relationships

2 IMPORTANT ASPECTS OF EXPERIMENTAL RESEARCH

• Independent variable (treatment) • Dependent variable (outcome)

2 VARIABLES IN EXPERIMENTAL RESEARCH

The researcher manipulates the independent variable. They decide the nature and the extent of the treatment. After the treatment has been administered, researchers observe or measure the groups receiving the treatments to see if they differ. Experimental research enables researchers to go beyond description and prediction, and attempt to determine what caused effects.

4 MAJOR CHAR OF EXPERIMENTAL RESEARCH

• The Matching-Only Design

An alternative to random assignment of subjects but never a substitute for random assignment.

Multiple Regression The Coefficient of Determination The Coefficient Multiple Correlation

COMPLEX CORRELATIONAL TECHNIQUES

• Subject Characteristics • Mortality • Location • Instrument decay • Date Collector Characteristics • Data Collector Bias • Testing • History • Maturation • Attitudinal • Regression • Implementation

Controlling Threats to Internal Validity (12) (S, M, L, I, D, D, T, H, M, A, R, I)

TRUE OR FALSE

Correlational research, like causal comparative research, is an example of what sometimes called associational research.

TRUE Q

EXPLANATORY STUDIES Although the discovery of a correlational relationship does not establish a causal connection, most researchers who engage in correlational research are probably trying to gain some idea about cause and effect.

TRUE

EXPLANATORY STUDIES It must be stressed, however, that correlational studies do not, in and of themselves, establish cause and effect

Discriminant Function Analysis

In most prediction studies, the criterion variable is quantitative that is, it involves scored that can fall anywhere along a continuum from low to high.

Time-Series Design

Infrequently used due to extensive amount of data collection.

FACTOR ANALYSIS

It is often desirable, therefore, to reduce the number of variables by grouping those that are moderately of highly correlated with one another into factors.

• Randomization • Hold certain variables constant • Build the variable into the design • Matching • Use subjects as their own control • Analysis of Covariance (ANCOVA)

Most Common Ways to Eliminate Threats (6)

Explanatory Studies Prediction Studies

PURPOSE OF RESEARCH (2)

• The One-Shot Case Study • The One-Group-Pretest-Posttest Design • The Static-Group Comparison Design

Poor Experimental Designs (3)

• The Matching-Only Design • Counterbalanced Design • Time-Series Design

Quasi-Experimental Designs

Scatterplots Simple Prediction Equation

SIMPLE CORRELATION TECHNIQUES (2)

TRUE

TRUE OR FALSE EXPLANATORY STUDIES A major purpose of correlation research is to clarify our understanding of important phenomena by identifying relationships among variables.

TRUE

TRUE OR FALSE The experimental group receives a treatment of some sort while the control group receives no treatment.

TRUE

TRUE OR FALSE EXPLANATORY STUDIES Variables found not to be related or only slightly related are then dropped from further consideration, while those found to be more highly related often serve as the focus of additional research, using an experimental design, to see whether the relationship are indeed causal.

TRUE

TRUE OR FALSE Researchers who conduct explanatory studies often investigate a number of variables they believe are related to a more complex variable, such as motivation or learning.

The Coefficient Multiple Correlation

The coefficient of multiple correlation, symbolized by R, indicates the strength of the correlation between the combination of the predictor variables and the criterion variable. It can be thought of as a simple Pearson correlation between the actual scores on the criterion variable and the predicted scores on that variable.

Counterbalanced Designs

The effectiveness of the various treatment can be determined by comparing the average score for all groups on the posttest for each treatment.

The Coefficient of Determination

The square of the correlation between a predictor and a criterion variable is known as the ....

predictor variable

The variable that is used to make the prediction

1. It takes place before the experiment begins 2. Process of assigning the groups takes place 3. Groups should be equivalent

Three things occur with random assignments of subjects:

• The randomized Posttest-only Control Group Design • The Randomized Pretest-Posttest Control Group Design • The Randomized Solomon Four-Group Design

True Experimental Designs

FACTOR ANALYSIS

When a number of variables re investigated in a single study, analysis and interpretation of data can become rather cumbersome

Correlational study

describes the degree to which two or more quantitative variables are related, and it does so by using a correlation coefficient.

• Statistical Matching

does not necessitate a loss of subjects, nor does it limit the number of matching variables.

experimental research

however there is no manipulation of variables in correlational research.

PREDICTION

if a relationship of sufficient magnitude exists between two variables, it becomes possible to predict a score on the other variable is known.

Correlational studies

investigate the possibility of relationships between only two variables, although investigators of more than two variables are common.

• Random assignments

is a powerful tool for controlling threats to internal validity.

• Mechanical Matching

is a process of pairing two persons whose scores on a particular variable are similar.

FACTOR ANALYSIS

is a technique that allows a researcher to determine if many variables can be described by a few factors.

Correlational research

is also sometimes referred to as form of descriptive research because it describes an existing relationship between variables.

Path analysis

is used to test the likelihood of causal connection among three or more variables. Some of the other techniques we have described can be used to explore theories about causality, but path analysis are far more powerful than the rest.

Random assignment

means that every individual who is participating in the experiment has an equal chance of being assigned to any of the experimental or control groups.

Random selection

means that every member of a population has an equal chance of being selected to be a member of the sample.

association research

the relationship among two or more variables are studied w/o any attempt to influence them.

criterion variable

variable about which the prediction is made is

Time-Series Design

• After multiple measurements, experimental treatment is administered (or occurs naturally).

Time-Series Design

• After the treatment, periodic measurements are continued in order to determine the treatment effect.

Counterbalanced Designs

• Each group is exposed to all treatments but in a different order.

• The Randomized Solomon Four-Group Design

• Four groups used, with two pre-tested and two not pre-tested.

Time-Series Design

• Involves periodic measurements on the dependent variable for a group of test units.

CONTROL EXTRANEOUS VARIABLE

• It is the responsibility of the researcher to control for possible threats to internal validity.

• The Matching-Only Design

• Random assignment is not used.

CONTROL EXTRANEOUS VARIABLE

• The researcher has the ability to control many aspects of an experiment.

Time-Series Design

• The threats to internal validity- history, instrumentation, and testing.

CONTROL EXTRANEOUS VARIABLE

• This is done by ensuring that all subject characteristics that might affect the study are controlled