Literature review - a step-by-step process that involves the identification of publishes and unpublished work from secondary sources on the topic you are interested in - the evaluation of this work in relation to the problem and documentation of it.
It helps you develop a good problem statement: ensures that no important variable are overlooked in the process of defining the problem.
Other functions:
1. prevent waste of resources in reinventing wheel.
2. Fascilitates the creative integration of the information gathered from the structured and unstructured interviews.
Thus - it provides the foundation for developing a comprehensive theoretical framework from which hypothesis can be developed for testing.
Good literature review ensures:


1. important variables are not left out.
2. a cleared ideao emerges as tow hat variable will be most important to consider, problems - helps the development of the theoretical framework and hypothesis for testing.
3. Problem statement - made with precision and clarity
4. Testability and replicability are enhanced
5. Avoid reinventing the wheel
6. Problem being investigated is perceived by the scientific community as relevant and significant.