The researcher evaluates the paper and often compares it with other works on the same subject.
Critical abstracts are generally 400-500 words in length due to the additional interpretive commentary. A descriptive abstract indicates the type of information found in the work.
The length varies according to discipline, but an informative abstract is usually no more than 300 words in length.
A highlight abstract is specifically written to attract the reader’s attention to the study.
How do you know when you have enough information in your abstract?
A simple rule-of-thumb is to imagine that you are another researcher doing a similar study.
That is, the researcher presents and explains all the main arguments and the important results and evidence in the paper.
An informative abstract includes the information that can be found in a descriptive abstract [purpose, methods, scope] but it also includes the results and conclusions of the research and the recommendations of the author.
In most cases, the abstract page immediately follows the title page. Rules set forth in writing manual vary but, in general, you should center the word "Abstract" at the top of the page with double spacing between the heading and the abstract.
The final sentences of an abstract concisely summarize your study’s conclusions, implications, or applications to practice and, if appropriate, can be followed by a statement about the need for additional research revealed from the findings.