SAT scores and college achievement, Experimental design

2. a. Discuss two main advantages and two main disadvantages of doing co relational research?

Correlational research is very effective in under scoring the trends in covariance of two more factors having a positive or a negative link between them. but, often times, researchers may get mistaken and take the superficial correlation, as a causal explanation for the two variables being positively or negatively related.

In case that such data leads to analysis of the research experiment, results and the following discussion can be flawed. To avoid that, it is best that the co relational research designs are used carefully and no causal statement re made, unless there is concrete support that can allow the researchers to present two variables as being causal.

By the very nature of multivariate research design, and presence of multiple variables, confounding factors will naturally be something to be careful about and there can be situations in which it will be best to not state that causal relationship is established between two studied variables' and their interaction.

b. Give an example of two variables that you think are negatively correlated with

each other and explain why you think so.

positive correlation example (SAT scores and college achievement?among college students, those with higher SAT scores also have higher grades)

negative correlation example (Crying and being held?among babies, those who are held more tend to cry less (or phrased as babies who are held less tend to cry more))

3. a. What are three essential characteristics of an experiment?

A problem statement or an experimental hypothesis
Experimental design must have sample
Variables - independent and dependent to be studied

b. Why and how is each of these important for the validity of an experiment?

Validity refers to the ability of a prediction statement, or the selected sample and variables, to be feasible for a designed experiment and its successful conclusion after the study and the analysis phases are done.

For the validity of any scientific experiment, a hypothesis statement is essential, so that there is a purposefulness behind conducting the research.

Experimental design has to be 'valid' so that it can sustain the significance test that helps to ascertain whether the stated or predicted hypothesis is true or not.

Without a solid hypothesis and variables that are selected to predict the interaction or effect of each other, for the proper study in an experimental design, the research cannot be deemed as useful.

References

http://departments.vassar.edu/~lowry/ch3b.html
step.psy.cmu.edu/schunn/lectures/1introduction.ppt

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