IF with AND: both conditions must hold

AND takes any number of tests and is true only when every one of them is true. Dropped inside an IF, it turns a single condition into a rule with several parts: =IF(AND(test1,test2),"yes","no").

The failure to watch for is reaching for OR. OR is true when at least one test passes, which is a much easier bar, a rep with huge sales and terrible returns sails through it. The two words are not interchangeable and the difference is money.