2. Relationship or difference studies
correlational
pearson r
advantages and disadvantages
developmental studies: advantages & disadvantages
*As the title notes this type of study traces the relationships or differences between variables to gain a greater depth or understanding about phenomenon = correlational & developmental studies
- A.Correlational studies: looks at relationships. The researcher looks to see if one variable changes how the other variable changes. Looking at quantifying the strength of the relationship between variables or in testing a hypothesis about a specific
- relationship. The relationship can be positive or negative.
This is done with the Pearson r correlation coefficient.
Pearson r
*This is a statistical test that is calculated to reflect the degree of relationship between 2 variables (p. 355).
*Once the r is calculated the researcher reports the value of the correlation & the probability of it occurring by chance.
*Correlation coefficients range in value from -1.0 to +1.0. The value in between of 0 indicates that there is NO relationship between the variables.
*+1 is a perfect positive relationship. -1 is a perfect negative relationship.
*Example: I am interested to know the correlation between the age of a patient & the time required to recover from surgery.
- *A Pearson correlation test shows that r = +.76 at p = 0.025. From this I know that there is strong positive relationship or if
- one is older the more recovery days. The low p values tells me that my result is statistically significant or the probability of the test result occurring by chance is very low or the probability of the negative strong negative relationship is high. The values of the r & p are considered together.
Advantages:
*↑flexibility when investigating complex relationships between variables.
*Efficient & effective method of collecting a large amount of data.
*Potential for practical application in clinical settings.
*A potential foundation for future experimental studies.
*A framework for exploring the relationship between variables that cannot be manipulated.
Disadvantages:
*The variables cannot be manipulated.
*Randomization is not used thus generalizability is decreased.
*Casual relationships cannot be made because of reduced controls, manipulation or randomization.
B.
Developmental studies
These types of studies use a time perspective or the changes that occur from elapsed time.
1.
Cross-sectional studies: data is collected on participants at 1 point in time. Less costly & time consuming than longitudinal studies. Not affected by maturation.
2.
Longitudinal or prospective studies (repeated measures): data collected from the same group at different points in time. They are costly in regards to time, money & effort. Hawthorne effect & maturation are threats. They begin in the present & end in the future.
3.
Retrospective or ex post facto (after the fact) studies: the DV has already been affected by the IV. The researcher attempts to link present events to events that have occurred in the past. See model below.
Advantages:
*Important designs when randomization, control & manipulation are not appropriate or possible.
*Useful in testing theoretical models of how variables work together in a group in a particular situation.
*Important to develop knowledge base on phenomenon of interest.
*Useful in forecasting or making predictions.
Disadvantages:
*Difficulty explaining cause-and-effect or causal relationships.
*Challenging to find groups that are similar in extraneous variables (ex facto studies).