Bayesian Classification

Metode Bayesian

(Studi Kasus : Prediksi)

Jika terdapat sebuah tabel berisi data permainan tenis seperti berikut :

dan kondisi cuaca saat itu (Datum) adalah :

- Outlook : Sunny

- Temperature : Cool

- Humidity : High

- Wind : Strong

Pertanyaan : apakah seseorang tersebut akan bermain tenis? (Yes atau No)

Jawaban :
Rumus Bayesian : P(h | d) = [P(d | h) . P(h)] / P(d)

1. Menghitung probabilitas "Sunny & Play" :
• P(Sunny | Play) = P(Sunny ∩ Play) / P(Play) = 2 / 9 = 0.22
2. Menghitung probabilitas "Sunny & Not Play" :
• P(Sunny | -Play) = P(Sunny ∩ -Play) / P(-Play) = 3 / 5 = 0.6
3. Menghitung probabilitas "Cool & Play" :
• P(Cool | Play) = P(Cool ∩ Play) / P(Play) = 3 / 9 = 0.33
4. Menghitung probabilitas "Cool & Not Play" :
• P(Cool | -Play) = P(Cool ∩ -Play) / P(-Play) = 1 / 5 = 0.2
5. Menghitung probabilitas "High & Play" :
• P(High | Play) = P(High ∩ Play) / P(Play) = 3 / 9 = 0.33
6. Menghitung probabilitas "High & Not Play" :
• P(High | -Play) = P(High ∩ -Play) / P(-Play) = 4 / 5 = 0.8
7. Menghitung probabilitas "Strong & Play" :
• P(Strong | Play) = P(Strong ∩ Play) / P(Play) = 3 / 9 = 0.33
8. Menghitung probabilitas "Strong & Not Play" :
• P(Strong | -Play) = P(Strong ∩ -Play) / P(-Play) = 3 / 5 = 0.6
9. Menghitung probabilitas "Play" :
• P(Play) = 9 / 14 = 0.64
10. Menghitung probabilitas "Not Play" :
• P(-Play) = 5 / 14 = 0.35
11. Menghitung probabilitas "Sunny, Cool, High, Strong & Play" :
• P(Sunny, Cool, High, Strong | Play) = 0.22 x 0.33 x 0.33 x 0.33 x 0.64 = 0.005
12. Menghitung probabilitas "Sunny, Cool, High, Strong & Not Play" :
• P(Sunny, Cool, High, Strong | -Play) = 0.6 x 0.2 x 0.8 x 0.6 x 0.35 = 0.02

Kesimpulan : 

Karena nilai probabilitas P(Sunny, Cool, High, Strong | -Play) > P(Sunny, Cool, High, Strong | Play), maka hasilnya adalah "No" atau orang tersebut tidak bermain tenis (Not Play)