Home › SMLE (Saudi Medical Licensing) › Epidemiology and Biostatistics › Measures of Risk › A risk ratio of 0.28 for vaccinated against unva…
A risk ratio of 0.28 for vaccinated against unvaccinated children means what?
AVaccination raised risk by roughly one quarter
BVaccination changed risk by no measurable amount
CVaccination cut risk by roughly three quarters
DVaccination raised risk by almost four times over
Answer & Solution
Correct answer: C. Vaccination cut risk by roughly three quarters
1. A risk ratio of 1.0 means identical risk in the two groups.
2. A value below 1.0 means the group in the numerator, here the vaccinated children, carries the lower risk.
3. 0.28 means vaccinated children ran about 28% of the risk of unvaccinated children, a cut of roughly three quarters.
4. No measurable difference would show as a ratio near 1.0, not 0.28.
5. A ratio near 4.0 would be needed for a fourfold increase, and any increase at all needs a value above 1.0.
_Source: CDC Principles of Epidemiology in Public Health Practice (3rd ed., US federal, public domain), Lesson 3 "Measures of Risk", section Definition of risk ratio_
Related questions
Among wedding guests, 50 of the 53 who ate cake became ill. What does the fraction 50 overVaricella struck 11.8% of vaccinated children and 42.9% of unvaccinated children. What is What distinguishes vaccine efficacy from vaccine effectiveness?At a wedding, 50 of 53 cake eaters and 4 of 26 non-eaters fell ill. What share of illness Lung cancer mortality was 0.57 per 1,000 per year among light smokers and 0.07 among nonsmInfirmary visits for acute respiratory illness ran at 11.6 per 1,000 tourists per week in Why is the odds ratio the measure of choice in a case-control study?In a case-control study, 32 of 40 case-patients and 20 of 80 controls had stored maize ind