How to calculate progressives?

[razuberii]

Hi guys,
Up in No Cali, I came across a bank of 12 progressive $1 machines.  It has JoB 9/6, DW NSUD and DDB 9/6.  How do I calculate when the progressive turns positive?  Also, does strategy change?
 
The jackpot was up to $5528.
 
Thank you
 

[New2vp]

There are generally strategy changes.  But if you don't know them and you come across games that are positive, just using regular strategy will be fairly close most of the time, until you have the time to work out the changes.  You could also work out changes in advance for a few different levels, say 4500, 5000, 5500, so you can be ready when you something good.To find the point at which a game turns positive, you can use trial and error on poker software by increasing the royal payoff.  Take DDB 9/6 as an example and start with the royal at 4000.  Let g = game return and r = royal return.  The necessary royal payoff (y) without changing strategy is y = 4000 x (1-g +r) / r.  In this case, y = 4000 x (1 - .989808 + .019608) / (.019608) = 6079.But with a payoff of 6079, strategy will change, so you then need to check for strategy changes.  This means the final answer will be somewhat reduced at a later step.  (If you put this in an Excel spreadsheet, you can continually copy the statistics into the same place in your worksheet to reduce calculation time.)Using 6079, you get y = 6079 x (1 - 1.001344 + .035107)/ .035107 = 5846.Putting 5846 into the formula, you get y = 5846 x (1 - 1.000000 + .033669) / .033669 = 5846.  When you get what you start with or you get 100.0000% return you are done.  So, the answer for DDB 9/6 is 5846.Similarly, JOB 9/6 is 4880 and NSUD is 4587.Most would rather look at http://www.videopokerhelp.net/condensed-prog.htm, where the calculations have already been done for you for a large number of common games.Based on what you said the progressive jackpot had increased to, NSUD has the best EV.  If you have a choice of games, as a rule of thumb, play the game that has the best EV with the normal 4000 jackpot.  Good luck.

[razuberii]

New2vp~ thanks for the formula assistance.
I'll take a peek at videopokerhelp~ didn't know it existed. 
Thanks a $$million (or at least~ a progressive RF~)