Systematic Literature Review – Combining your search strings to create your search strategy
Previous posts have looked at the following steps in the systematic literature review:
This post will discuss combining your search strings to create your search strategies.
Once you have your search strings, the next step in your process is to search for combinations of the search strings, so that you can find the bodies of literature which deal specifically with aspects of your research topic. You can use the Boolean operators AND, OR and NOT to combine the search strings. Be wary of using the NOT operator as this will exclude any of the words in the NOT string from your search, and may mean that relevant articles are inadvertently excluded. If we take the search strings from our previous post as an example, relevant articles might be found by searching for:
String 1 and String 2
(“supply chain*” OR “supply network*” OR “demand chain*” OR “demand network*” OR “value chain*” OR “value network*”) AND (“lead time compression” OR “lead time reduction” OR “cycle time compression” OR “cycle time reduction” OR “dwell time compression” OR “dwell time reduction”)
String 1 and String 3
(“supply chain*” OR “supply network*” OR “demand chain*” OR “demand network*” OR “value chain*” OR “value network*”) AND (agil* OR “quick response” OR speed*)
String 2 and String 3
(“lead time compression” OR “lead time reduction” OR “cycle time compression” OR “cycle time reduction” OR “dwell time compression” OR “dwell time reduction”) AND (agil* OR “quick response” OR speed*)
String 1 and String 2 and String 3
(“supply chain*” OR “supply network*” OR “demand chain*” OR “demand network*” OR “value chain*” OR “value network*”) AND (“lead time compression” OR “lead time reduction” OR “cycle time compression” OR “cycle time reduction” OR “dwell time compression” OR “dwell time reduction”) AND (agil* OR “quick response” OR speed*)
The diagram below illustrates how your strings above could be put together.
Which fields should I search in?
Generally speaking, researchers should search the Abstract, Title and Keyword fields when carrying out their systematic review. Searching the Full-Text field may produce too many results, and reduce the relevance. Restricting to just one of the fields mentioned above, may produce too few results.
I’m receiving too many results…
If your search retrieves too many items, the AND operator can be replaced by a proximity operator, e.g. n/3 or w/3. The n (or w) signifies that words in the string following should appear within the next 3 words of the initial string. The n will look for the keywords in your second string on either side of your first string terms. The number 3 can be replaced by any number of your choosing. Using a proximity operator will make the search more precise and retrieve fewer documents. Not all databases have the proximity operator option and the way they are entered may vary e.g. ABI/Inform uses w/5 while EBSCO uses w5.
Carrying out a systematic literature review is an iterative process, and to do it well takes a great deal of time. Simply identifying the keywords and search strings can take several attempts and requires a great deal of patience. You may think you have the perfect search strings but then find that they produce too many results or none at all. If this is the case something may have gone wrong either in terms of the keywords being used, the way they are being combined to make a search string or the way in which the search strings are being combined.
Sometimes the only way to identify this is to systematically go through each search string one at a time, removing and adding words until the problem is identified. Alternatively, you may not have understood the way in which the database you are using works – are you using the correct operators? Are you searching the appropriate fields? Have you forgotten the quotation marks around phrases?
Other blog posts you may find useful
- Systematic Literature Review – Where do I begin?
- Systematic Literature Review – Selecting your sources
- Systematic Literature Review – Identifying your search terms and constructing your search strings
- Systematic Literature Review – Using Excel to help manage references for the systematic literature review process
Because of the complexity of this process we would recommend that before embarking on a systematic literature review you come and speak to a member of the MIRC team who will be happy to guide you through the process.
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