1. Lack of relevance e.g. of time, place, methods used, focus of study, etc.
2. possible weaknesses in the methodology e.g. small sample, sampling method, lack of control group etc.
3. possible flaws in the data analysis used 
areas which have not been examined i.e. a ‘gap’ in the literature
4. possible faulty logic e.g. the claims made are not based on the results 

1. strengths in the research design or data analysis
2. relevance of the study to your own research e.g. because it is similar in scale, focus, the participants, research context or design of the research
3. theories or ideas which may be particularly useful to your own research e.g. in the questionnaire 

1. Lack of relevance e.g. of time, place, methods used, focus of study, etc.
2. possible weaknesses in the methodology e.g. small sample, sampling method, lack of control group etc.
3. possible flaws in the data analysis used 
areas which have not been examined i.e. a ‘gap’ in the literature
4. possible faulty logic e.g. the claims made are not based on the results 

1. strengths in the research design or data analysis
2. relevance of the study to your own research e.g. because it is similar in scale, focus, the participants, research context or design of the research
3. theories or ideas which may be particularly useful to your own research e.g. in the questionnaire 

A set of reasons or a logical basis for a course of action or belief.

Mid 17th century: modern Latin, neuter (used as a noun) of Latin rationalis ‘endowed with reason’ (see rational).

Cambridge Dictionary
rationale
noun [ C or U ] UK ​ /ˌræʃ.əˈnɑːl/ US​ /ˌræʃ.əˈnæl/ formal

I don't understand the rationale for these restrictions.

He tried to explain the scientific rationale behind his work.

Collins Dictionary
rationale

(ræʃənɑːl  , -næl)

Word forms: plural rationales 

countable noun
The rationale for a course of action, practice, or belief is the set of reasons on which it is based.

[formal]However, the rationale for such initiatives is not, of course, solely economic. [+ for]
The rationale of reprocessing spent nuclear fuel is inevitably being questioned.
Synonyms: reason, grounds, theory, principle   
Chinese: 全部理由

Rationale + research + definition (from Google):
A rationale for research is a set of reasons offered by a researcher for conducting more research into a particular subject -- either library research, descriptive research, or experimental research.

FY

1.       To what extent do people have the awareness of global warming?

2.       What is the major trigger for global warming?

3.       Are there any effective suggestions to reduce the greenhouse gas emission?

Questionnaire B               

1.       What attitudes do customers hold towards store brands?

2.       What factors influence customers’ general attitudes and perceptions towards store brands?

3.       Do different age groups have different attitudes towards store brands?

1.       What are some of the positive and negative attitudes towards organic food?

2.       What variables affect these attitudes?

3.       What are the main barriers to influencing organic customers’ behaviour in Glasgow?