While browsing Internet, I stumbled upon a web site at http://www.mcli.dist.maricopa.edu/proj/res_meth/rmvl/index.html, which has provided useful information regarding research methods. My notes are as follows:
1. Experimental: This method is one in which a researcher manipulates an independent variable (anything that can vary) under highly controlled conditions to see if this produces (causes) any changes in a dependent variable. He has to ensure holding all other variables, variables that might also affect the dependent variable, constant. The method can help in determining cause-and-effect relationships. A major limitation is that this method can only be used when it is practical and ethical for the researcher to manipulate the independent variable.
2. Following four research methods are called as descriptive methods. Use of these methods does not allow drawing conclusions about cause-and-effect relationships but can be used where experimental method cannot be used.
a. Correlation: This method helps determine the degree and direction of relationship between two or more variables or measures of behavior. It also can be used as a basis for prediction.
b. Naturalistic observation: In this method, the researcher very carefully observes and records some behavior or phenomenon, sometimes over a prolonged period, in its natural setting.
c. Survey: Surveys are particularly useful when researchers are interested in collecting data on aspects of behavior that are difficult to observe directly (such as thoughts about suicide) and when it is desirable to sample a large number of subjects. Since it relies on a self-report method of data collection, intentional deception, poor memory, or misunderstanding of the question can all contribute to inaccuracies in the data.
d. Case Study: It involves an in-depth descriptive record, kept by an outside observer, of an individual or group of individuals. They often rely on descriptive information provided by different people. This leaves room for important details to be left out. Also, much of the information collected is retrospective data, recollections of past events, and is therefore subject to the problems inherent to memory.
The site also provides more details, which you may find useful if you are interested in this area.