Probability BasicsATI TEAS 7 cheat sheet

Favorable over total

8 key facts Reviewed Oct 2026

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The Formula

P = favorable outcomes / total outcomes
Always between 0 and 1 (or 0–100%)
P = 0 impossible, P = 1 certain

Complement

P(not A) = 1 − P(A)
Often far faster than counting the event itself

Independent Events

Both happen → multiply the probabilities
Coin then die: ½ × ⅙ = 1/12

With Vs Without Replacement

Without replacement, the total shrinks for the second draw

Key takeaway

Favorable over total

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