There is still much argument concerning whether the word ‘data’ is singular or plural. In Latin, ‘data’ is the plural of ‘datum’. Historically, this has been true in English. However, in modern, non-scientific use, it is usually treated as a mass noun, similar to ‘information’, which cannot normally have a plural and which takes a singular verb. 

In modern English, sentences such as “This data is misleading” are now widely accepted, although the purists and pedants are still fighting a rearguard action against this trend.

My advice is to treat the word as a mass noun in normal writing. If you’re referring specifically to scientific data or writing for conservative publications, treat it as a plural. Treating ‘data’ as a plural is never wrong, but it may look and sound wrong to modern English users.

If in doubt, in many cases you can replace ‘data’ with ‘information’ and please everyone.