For the Math Wizards

[BigBill]

While playing online Blackjack how often should the dealer have a made
2 card hand (17-18-19-20-21) and should I in the long term expect the
percentage to equal out?

[awstick]

It would depend on if the dealer stands on soft 17 and how many decks are used.

[aka23]

While playing online Blackjack how often should the dealer have a made
2 card hand (17-18-19-20-21) and should I in the long term expect the
percentage to equal out?

Roughly 35% for a 2 card hand.

Roughly 70% for the final hand. However, he may appear to bust less than 30%, as sometimes you bust before the dealer. With basic strategy, he'll bust closer to 25% of the time.

Regarding expecting the long term percentage to equal out, it depends how many hands are played. You can calculate how many standard deviations the results are from the mean.