It is not always necessary to collect all the data yourself. You may also use existing sources. Think of databases like SCP or CBS, from which you can buy data, but also from your own administration or cash register system. Use existing databases if you want to know more about a particular subject on which national data is collected or if you require quantitative data about your own organization. A lot of data is readily available. Just make clever use of this.

TIPS

1. Formulate a clear purpose and research question and sub-questions that you seek answers to with existing research sources.
2. Provide keywords and search terms derived from your purpose and research question. This will give you a clear direction to look for relevant sources.
3. Collect current information.
4. Make sure the sources are relevant to your problem statement.
5. Keep track of which information you get from where, so you and your client can see which sources were used.
6. The information provided by existing data sources does not always fully match the problem statement or might be incomplete. In such cases, it is wise to combine existing source research with other research methods.

In literature research, you research readily available data to formulate a problem definition. Some cases have been studied before, and there is no need to reinvent the wheel. By doing literature research, you can gather a lot of information. I will give you eleven tips for doing literature research:

1. Much information is already available. Through literature review, you can gather a lot of information about trends, market movements, market structure, and developments without having to do the fieldwork.
2. The literature review will form a clear purpose/research question and sub-questions that you want the answers to.
3. Provide keywords and search terms derived from your purpose/research question. This will give you a direction to research relevant literature.
4. Look for references and source citations to other publications in relevant articles. This will give you what is known as the snowball effect to new information.
5. Gather current information.
6. Turn the collected literature into one document, adding only the relevant information that answers the research question.
7. Keep track of what information you get from where, so you and your client can see which sources were used.
8. Mention the sources using the APA rules to avoid plagiarism.
9. Important when you are doing desk research is to check the relevance of the data. Does this information answer your problem definition?
10. Ensure to have multiple sources. This makes the data more reliable.
11. Provide reliable sources, such as (scientific) articles through Google Scholar, published studies on official websites, or sources from the library.

The validity of a study explains the extent to which the questions asked measure what they are supposed to measure. In other words, are the questions asked unambiguous. Could the respondent have interpreted the question differently than you had intended it? And regarding the questionnaire as a whole: do the questions asked in the questionnaire answer the research question.

By challenging a questionnaire, you can find out if it is valid. You can do this by presenting the questionnaire to a test person and having them think out loud while completing it. Another possibility is to present the questionnaire to a test group and have them ask questions as soon as a question is unclear. It is essential that your test persons/group resemble your research population. So if you want to present the questionnaire to young people aged 15 to 18, your test persons/group should consist of young people aged 15 to 18.

After this test, especially with a test group, analyze the answers and ask for advice from a fellow researcher. Are the answers consistent? Is the logic within the questionnaire correct? Are the results consistent with similar studies?

It is more important to test, adapt, and retest with newly developed research instruments. Especially if you want to measure more abstract concepts such as attitude or development, extensive testing is needed to get a valid questionnaire.

When using an existing questionnaire, you should take a moment to see if it has already been tested for comprehension and consistency.

In addition to validity, the concept of reliability is often discussed when conducting research. Want to know more about this? Also read my blog about reliability.