How to Create Grading Formula

Dear all,

Could anyone please help me to create a simple formula that will output a score between 0 and 15 for a series of YES/NO answers to a series of 15 questions.

For example, I have 15 questions, each requiring a YES/NO answer.
The answers are then inputby students into a single row of an excel spreadsheet.
I have the correct answers to the YES/NO questions.

E.g.,

STUDENT ANSWER: YES YES YES NO YES NO YES NO NO NO YES NO YES NO YES

MY ANSWERS: NO YES NO YES NO NO YES YES NO YES NO NO YES YES NO

STUDENT'S SCORE =

What formula can I use to output a score between 0 and 15 for the student?

Many thanks for your help and assistance.

Best wishes.
Max

If answers is in cells B1, B2, ..., B15 in cell B16 formula is =countif(B1:B15;"YES") for answer YES.
If you wish answer as procent that formula is =countif(B1:B15;"YES")/15 and format cell B16 as procent.