AVG(CASE) Statement - Help Please

I am trying to get avg score by site, by call type. Columns are Site(varchar), Calltype(varchar), totalscore(float). Calltypes are A, B, C, D. Sites are 1, 2, 3, 4. I can do a straight average statement and only get one calltype.
I want to do a CASE statement to get all average scores for all calltypes.

Select Site, avg(totalscore) as [Avg Score]
FROM DB
WHERE calltype = 'A'
GROUP BY Site

Results

Site Avg Score (for A)
1 85
2 75.5
3 85.33

SELECT Site, AVG(CASE WHEN TotalScore > 0 AND CallType = 'A' THEN Totalscore
ELSE 0 END) AS [Avg Score For A]
FROM DB
GROUP BY Site

Results

Site Avg Score For A
1 i get 8.5
2 i get 37.75
3 i get 36.57
Why am I getting a difference?
Any help is greatly appreciated - thank you

the problem is in the way you write your avg case.
simply remove the else 0 and you will have the same result.

When using the else 0 you are basically increasing the number of rows that match the casetype = 'A' because you replace a null value with 0.