"A large number of tests has (or have?) been conducted. What should it be? Regards NSP"
"This is really a tricky one. I am eager to know the rule of grammar that governs such sentence construction. I feel it should be 'has' because it is 'A large number'.. and may be 'have' because of 'tests'.. not clear??? can anybody help?"
Both are possible, depending on whether the emphasis is on "number" or on "tests".
Regards, Einde O'Callaghan
P.S. I think I answered this question - or a similar one - recently either here or in another newsgroup.