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UJI CHI-SQUARE .

Sumedi Sudarsono

Untuk menguji hubungan antara dua variabel

qualitatif. Tabel 2 x 2, 2 x 3, 3 x 3, dsb.

Diare Tidak Total----------------------------------------------

Es buah 22 78 100 (baris 1)

Tidak 10 80 90 (baris 2)

-----------------------------------------------

Total 32 158 190

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Tabel 2 x 2

Diare Tidak Total

----------------------------------------------

Es buah a b (a+b) (baris 1)Tidak c d (c+d) (baris 2)

---------------------------------------------

Total (a+c) (b+d) n(grand total)

(kolom 1) (kolom 2)

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Uji Chi-square.

1. Perhatikan Tabel. (Apa memenuhi syarat).

2. Ho : Tidak ada hub antara mkn es dg diare.

3. Tetapkan (alpha), 5% = 0.05

4. Hitung besar nilai Chi-square & df.

5. Tetapkan apakah Ho ditolak/diterima.6. Menarik kesimpulan.

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Syarat uji chi-square :

1. Sampel harus besar. (n > 30).

2. Sel-sel tidak boleh ada yg nol.

3. Expected sel-sel harus > 5.

Bila ada sel dg exp

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UJI CHI-SQUARE.

(a+b) (a+c)

Expected sel a = ------------------

n

(a+b) (b+d)

E(b) = -------------------

n

E(c) =

E(d) =

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UJI CHI-SQUARE .

(O E) 2

Rumus X2 = -----------

E O = ObservedE = Expected

(ad bc)2 nX2 = -----------------------------

(a+b)(c+d)(b+d)(a+c)

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UJI CHI-SQUARE.

O E O-E (O-E) 2 / E

------------------------------------------------------------

a =22 16.84 5.16 1.581

b =78 83.16 -5.16 0.320

c =10 15.16 -5.16 1.756

d =80 74.84 5.16 0.356

-----------------------------------------------------------

n = 190 Chi-square = 4.01

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Chi Square.

{22(80) 78(10)}2 (190)

X2

= ---------------------------------- = 4.01100 (90) (158) (32)

Degree of Freedom = (baris -1)(kolom -1)df = (2 1)(2 1) = 1

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Chi-square .

X2

= 4.01 0.025 < p < 0.05df = 1 Lihat Tabel Chi-square

p

df 0.25 0.10 0.05 0.025 0.010 0.001

-------------------------------------------------------------

1 1.32 2.71 3.84 5.02 6.63 10.83

2 2.77 4.61 5.99 7.38 9.21 13.82

3 .. .. .. .. ..

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Relative Risk = RR = Ie / Io

a/(a+b) 22 / 100RR = ------------- = --------------- = 1.98 = 2.

c/(c+d) 10 / 90

Atributable Risk = AR = Ie Io

AR = 22/100 10/90 = 11 per 100