Blackjack Counting Strategy Deviations and Index Plays

Question 1

What is an 'index play' or 'index number' in card counting?

Accepted Answer

A true count threshold at which to deviate from basic strategy

Answer

Index numbers are the true count values at which a counter should alter their basic strategy decision to maximize expected value.

Question 2

The most valuable single strategy deviation in Hi-Lo is widely considered to be:

Accepted Answer

Standing on 16 vs dealer 10 at high counts

Answer

Standing on 16 vs dealer 10 at a true count of 0 or above (the 'Illustrious 18' top play) has one of the largest impacts on player EV.

Question 3

According to the 'Illustrious 18,' at what true count should a player stand on 15 vs dealer 10?

Accepted Answer

+4

Answer

A player should stand on 15 vs dealer 10 when the true count reaches +4 or higher, as the deck is ten-rich enough to make standing profitable.

Question 4

When should a counter deviate to double down on 10 vs dealer Ace (instead of hitting)?

Accepted Answer

When true count is +4 or higher

Answer

Doubling 10 vs Ace becomes profitable at a true count of approximately +4, when the deck's ten-richness makes the double down worthwhile.

Question 5

What does 'fab four surrenders' refer to in blackjack counting?

Accepted Answer

Four surrender plays triggered by count that basic strategy doesn't include

Answer

The Fab Four are four late surrender deviations (e.g., 15 vs Ace, 14 vs 10) that become correct at specific true count levels.

Blackjack Counting Practice Test