The bidding has gone Pass - Pass – Pass, so it’s now up to you whether or not this board gets passed in. You have a marginal, will I or won’t I? sort of hand.
The PEARSON COUNT helps us here, also known as the rule of 15: Add your high card points to the number of spades in your hand. If this comes to 15 or more you should open the bidding. If it is less than 15 you should pass.
The logic: When the points are evenly divided between opposing pairs it is probable that the pair with a spade suit will prevail at the one or two level.
Say you have: ♠764, ❤ AJ2, ♦ KQ985, JT .
Pearson count is 11 + 3 = 14 so you should pass. By passing you prevent them coming in with a makeable spade overcall.
But with: ♠ JT976, ❤A6, ♦KJ8, Q75,
Pearson count is 11+ 5 = 16 so open 1 spade.
