a serial comma

[jc.analyst]

It is regarding a serial comma (also called Oxford comma and Harvard comma).

I am following APA style which recommends using a comma between elements (including before and and or) in a series of three or more items.

My query is this: In a single report, can i use this way only when there is ambiguity? OR Should I make it consistent and use this in all the places?

Thanks.

 

[iannou]

All things being equal, it makes sense to use it consistently throughout a single report. I'm not sure what kind of ambiguity you're referring to, but changing your comma usage within a single writing project seems more likely to create ambiguity than to alleviate it. The usage dictated by style guides is not generally treated on an "opt in/opt out" basis.