winning against higher rated players

Sometimes I loose to lower rated players around 750, and sometimes I win against 1175 players.  My average rating is 850.   How ?  why ?  any thoughts.  Have been playing for eight months.  

My view is that at a relatively low level (less than about 1100) both players are making blunders and their opponent is not even noticing half of the time (which is itself another blunder). The winner is often the person who, by chance, happens to make the fewest blunders or the least critical ones. 

So it is no surprise that you can lose against someone who is 700 one day and beat someone who is 1100 the next day. 

The answer is to make fewer blunders.

If you want me to look at a couple of your games and analyse your play to give some more specific advice just let me know.

Ratings are fluid.  They are just an average measure of a player's results.  Plus if a person hasn't played many games yet on the site their rating can fluctuate wildly, gaining or losing > 100 points in one game.

You relax more against lower rated players, and play worse against them, making your rating drop to their level. And when playing against stronger players the opposite happends. I have a problem with this as well

Well said Corum.

I agree with skotheim2, the psychological effort of trying to beat a virtually stronger player makes you play stronger, and understimating opponent will usually make you play "easier" and sometimes you'll end up making a blunder because you aren't as focused.

In my own personal experience, i have more than 1900 fide rate in classics, and i can make performances of 2.1 or even 2.2 on high rated tournaments, and then i can lose to a 1600 rated kid in a team match or standard tournaments because i literally blunder like there's no tomorrow.

On Chesstempo.com there is an option in settings that allows you to hide the rating of the opponent you are playing. I think it's pretty neat since it eliminates the problem of making preassumptions of your opponent based on the rating

I think the rating matchup would be better since even if your opponent has same  win/loss ratio he might still be significantly higher or lower level player. I don't think I would enjoy getting 2000 rated players against me 

Not that I can add much more to what were exceptionally good answers above (and helpful too! I also found I play much stronger when I'm against stronger players, even drawing on a few!) I also wonder about the time control -- were they live games or online?

Many interesting Variables.

I like the concept of hiding the rating. Maybe i would finally pay attention to the board instead of eating!!

Thank you all for the insight.  Over all I need to study more so I can teach my two children to play chess. 

My personal rule for OTB tournaments, and it probably works here too, is that ratings under about 1500 are not reliable--the person is probably not an extremely strong player (though if they are new or young, watch out!) but you cannot reliably expect 1200 to outplay 1000 the way you can expect 1900 to outplay 1700.

There are also personal variables.  My OTB club has one 1500 player who invariably outplays me--I have escaped with 2 wins and a draw but I was lost every game, and I'm an 1800 player.  I just don't handle his opening style well, or conversely he has an unusually good eye for my weaknesses.  (Drives me crazy!)  When two people sit down to play it's a complex mix of their fundamental strength, their current form, and the interaction of their styles:  rating is a vast oversimplification.

(The World Champion just lost to someone nearly 200 points below him--it happens to everyone at all levels from time to time.)