Using tenses consistently
You will use different tenses when describing different situations: established facts, a question needing an answer, describing your methods, reporting your results and what other researchers found and believe (or believed?). It can be confusing when you have a different tense in adjacent sentences or different tenses in the same sentence.
The key to getting tenses correct is to be consistent for different situations, as illustrated in the following abstract (key: present tense, past tense):
In people with randomenteric disease, symptoms improve using substance X. However, in 2016 Sigmund suggested that substance Y could be a better treatment. We performed a controlled trial to determine whether Y is more effective than X. We found that Y reduced symptoms in a greater proportion of people than X (y % vs. x %, p-value). We conclude that Y is more effective than X in treating people with randomenteric disease.
The present tense is used in the following situations:
- established fact
- the question asked (or hypothesis proposed) at the time of the study
- the answer and beliefs as a result of the study at that time.
The past tense is used in the following situations:
- attribution to previous work that is not yet established fact
- to describe your methods (what you did)
- to describe your results (what you found).
Some disciplines may use a different scheme, but the important point is to be consistent for the different circumstances.