We search for information on the internet all the time, but the kind of search you need for a systematic review is much more complicated than just typing keywords into a search engine like Google. To adequately and confidently address your question, you need to look for ALL pertinent empirical data, not just the most popular data or the data that’s easiest to find. On the other hand, you don’t want to waste time screening irrelevant citations, so you need a search that balances comprehensiveness with specificity.
That’s why you need an librarian. He or she will help you walk through these steps: