Hello Jean-Pierre Drolet,
Migration could cause you to get an average of 3.1 stars with two ratings. The old system was on a scale of 1-4. The new system is on a scale of 1-5.
For example:
Old Ratings = 3, 2
Old Average = 2.5
Scaled Ratings = 3*5/4 = 3.75, 2*5/4 = 2.5
Scaled Average = 6.25/2 = 3.125 = 3.1
As far as expecting seven ratings of four stars on this post, that is a different issue. Unfortunately, I no longer have access to the old system to see what it was rated before migration, so I can't really confirm or deny this.
The average ratings you see in your profile are calculated differently now than they used to be. The average you see in your profile is not an average of each individual rating you have received. Instead, it is the average of the average rating you have received on individual posts.
I know this is how it calculates the average for new ratings posted since November. I can't exactly remember how the migrated ratings were calculated in the profile - whether they were all averaged or if it was an average of the averages.
I hope I haven't confused things, and that I have cleared some things up. Sorry I couldn't help find your lost stars!
Thanks,
Molly K.
Web Support & Operations Manager
National Instruments