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metodologi penelitian dasar
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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
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