It is always important to assess the literature you are going to use in your assignment. Here are some tips on things to look for when you are assessing.

Things to think about when reading a study: could it lead to the wrong conclusion? Is there anything about the way the study is set up that seems strange to you, something that might lead to data bias, or pull the results in a certain direction? Could there be other reasons for the study’s findings, besides their own claims?

Examples of questions you can think about:

Is the article relevant in your field: topic, research question, study design, appropriate design, adds something new?
How have they measured effect? For questionnaires, look at: what questions have they asked?
Which participants are involved in the study? Are they representative for the group you want to say something about?
How many participants are in the study? How many were asked to participate, but declined? And how many people dropped out during the study?
Is the study financed by a commercial actor?
Are there are conflicts of interest?
When was the study conducted?
Is the article from a peer-reviewed journal?
What universities are the authors affiliated with, and what else have they published?
Has the article been retracted?

You can also search for the journal in Kanalregisteret (the Norwegian Register for Scientific Journals, Series and Publishers). Levels 1 and 2 mean that the journal fulfills the fundamental requirements for scientific publications.

Finally, do an overall assessment. If you are unsure, talk to your supervisor.

In the discussion section of the assignment, you will compare results from your included studies. Here, you are encouraged to look for a similarities between the studies, but it is also often interesting to discuss various reasons for different studies that reach contradictory conclusions.

Search & Write provides an introduction to Source assessment. Here, you can read about the principles involved in assessing a source for relevance and veracity.
The national research ethics committees have written an article about Different kinds of bias in research which can be interesting to read.
At kunnskapsbasertpraksis.no, you will find checklists for critically assessing research design.