Fix ponderated average computation

Also, fix default value inversion.

apachedex/__init__.py

@@ -455,10 +455,10 @@ class ERP5SiteStats(GenericSiteStats):
     date_dict = asDict(super(ERP5SiteStats, self).getApdexData())
     for date, (apdex, hit) in asDict(getDataPoints(self.no_module)
         ).iteritems():
-      super_apdex, super_hit = date_dict.get(date, (0, 100))
+      super_apdex, super_hit = date_dict.get(date, (100, 0))
       new_hit = hit + super_hit
       if super_hit:
-        new_apdex = super_apdex * new_hit / super_hit + apdex * new_hit / hit
+        new_apdex = super_apdex * super_hit / new_hit + apdex * hit / new_hit
       date_dict[date] = (new_apdex, new_hit)
     return sorted(((date, apdex, hit)
       for date, (apdex, hit) in date_dict.iteritems()), key=ITEMGETTER0)