วิธีการคำนวณ Probability Tools
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Probability measures the likelihood of an event, ranging from 0 (impossible) to 1 (certain). Combined probability tools calculate unions, intersections, and conditional probabilities for multiple events.
สูตร
P(A) = Favorable outcomes / Total outcomes | P(A and B) = P(A) × P(B) | P(A or B) = P(A) + P(B) − P(A and B)
- P(A)
- Probability of Event A (0 to 1)
- n
- Number of Outcomes (count)
คำแนะนำทีละขั้นตอน
- 1Complement: P(A') = 1 − P(A)
- 2Independent events: P(A∩B) = P(A) × P(B)
- 3Union: P(A∪B) = P(A) + P(B) − P(A∩B)
- 4Bayes' theorem: P(A|B) = P(B|A) × P(A) ÷ P(B)
ตัวอย่างที่มีคำตอบ
อินพุต
P(rain) = 0.4. What's P(no rain)?
ผลลัพธ์
0.6 (60%). Odds = 0.4/0.6 = 2:3
อินพุต
P(A)=0.01 (disease), P(B|A)=0.95 (test given disease), P(B)=0.10
ผลลัพธ์
P(disease|positive test) = 0.095 — only 9.5%
คำถามที่พบบ่อย
What does "independent events" mean?
Events are independent if the outcome of one doesn't affect the other. Rolling a die twice produces independent events.
What is conditional probability?
Conditional probability P(A|B) is the probability of A given that B has already occurred. It accounts for how new information changes odds.
What's the difference between theoretical and experimental probability?
Theoretical probability is calculated mathematically. Experimental probability comes from actual trials. With enough trials, they converge.