Vitri Widyaningsih

Faith_widy@yahoo.com

Public Health and Preventive Medicine Department

Universitas Sebelas Maret Surakarta

2014

VARIABEL

Sesuatu yang mempunyai nilai bervariasi

Karakteristik subjek penelitian yang memiliki nilai bervariasi

Misal : berat badan, tinggi badan, Hb dll

Variabel bebas

perlakuan, penyebab, pengaruh): menyebabkan perubahan variabel lain

Variabel terikat

(terpengaruh, akibat, efek) : yang berubah nilainya karena variabel bebas

Variabel ketiga (luar)

Macam Variabel dalam penelitian

Hubungan radiasi terhadap kelelahan mata Variabel bebas ? Variabel terikat?

Perbedaan tekanan darah pada pekerja terpapar bising dengan tidak terpapar bising Variabel bebas ? Variabel terikat?

Pengaruh kadar hemoglobin terhadap kelelahan dan produktivitas kerja Variabel bebas ? Variabel terikat?

Example

Variabel Perancu (Confounding)

Variabel Perantara (Intervening, Intermediate)

Variabel Interaksi (Effect Modifier)

Variabel Ketiga

Obesity Osteoporosis

Gender

Adiponectin

Genetic

VARIABLES

Confounder

Mediator (Intervening)

Effect Modifier (Interaction)

Confounding

A mixing of effects between the exposure, the disease, and a third factor associated with both the exposure and the disease such that the effect of exposure on the disease is distorted by the association between the exposure and the third factor

This third factor is so called confounding factor and can cause spurious association

The spuriousness arises from the effect of the first feature being mistakenly attributed to the second feature

Confounding can produce either a type 1 or a type 2 error, but we usually focus on type 1 errors.

Criteria for confounding

Influence outcome

Related to exposure

Not in the intermediate pathway

Confounding

Birth Order Down’s

syndrome

Maternal age

Observed (but spurious) association,

presumed causation

Unobserved

association

True

association

Cases of Down syndroms by birth order

0

20

40

60

80

100

120

140

160

180

1 2 3 4 5

Birth order

Cases per 100 000

live births

Apakah Ada Hubungan antara Urutan Kelahiran dan Risiko Sindroma Down?

Control for confounding

Randomization

Matching

Restriction

Stratification

Multivariable analysis

Hubungan kausalitas

1. Kronologi waktu (Time order)

2. Kekuatan asosiasi

3. Ada hub dosis response

4. Konsistensi

5. Biological plausibility

6. Bukti eksperimen

7. Kesamaan dengan hasil penelitian lain

Jenis Variabel (Murti B, 2007)

Kategorikal Kontinu

Nominal (Seks,

ras)

Interval

(Suhu skala C)

Dependen

(Ca rongga

mulut)

Independen

(Merokok)

Ordinal

(Stadium kanker,

kelas sosial)

Rasio

(denyut nadi,

elektrolit serum)

Jenis variabel

Variabel skala nominal

Nilai variasi tidak menunjukkan urutan

Contoh ; jenis kelamin (dikotomik), golongan darah (polikotomik), sarana transportasi, dll

Variabel skala ordinal

Order : bertingkat

Misal : tingkat pendidikan, tingkat pendapatan, stadium penyakit kanker

Variabel skala interval

Tidak memiliki nilai nol absolut

Misal : suhu (celcius), nilai ujian

Variabel skala rasio

Memiliki nol absolut

Misal : berat badan, tinggi badan, kadar obat, tekanan darah