A large segment of the population in your community smokes. In order to convince your patient population that it would be beneficial to quit smoking in order to prevent lung cancer, you conduct a casecontrol study of cigarette smoking and lung cancer. The results from that study can be found in the table below.What is the odds ratio (OR) in your study?
Answer(s): C
The OR is used when the denominator data are missing. It is calculated using the following formula, comparing smokers and nonsmokers:a x d / b x cIn this case, the mathematics is relatively simple: 75 x 75/25 x 25. By reduction, this is 3 x 3/1 x 1.
A large segment of the population in your community smokes. In order to convince your patient population that it would be beneficial to quit smoking in order to prevent lung cancer, you conduct a casecontrol study of cigarette smoking and lung cancer. The results from that study can be found in the table below.Using the same table, what is the relative risk?
Answer(s): E
A true risk ratio cannot be calculated from a case-control study.
A large segment of the population in your community smokes. In order to convince your patient population that it would be beneficial to quit smoking in order to prevent lung cancer, you conduct a casecontrol study of cigarette smoking and lung cancer. The results from that study can be found in the table below.Which of the following is most true concerning ORs and relative risk calculations, as pertaining to this study?
Answer(s): B
For ease of calculation, to illustrate the concept, the numbers in the question were kept simple. If the numbers of controls were increased, the difference would be smaller. The ORs are a reasonable estimate when denominator data are missing. Relative risk is determined when denominator data are available. Few case-control experiments have denominator data.
An investigator in a community hospital decides to examine all patients for a problem with alcoholism to determine prevalence in the community. In addition to recall bias, which of the following is the most obvious error in selecting all patients admitted to a community hospital?
Bias is a systematic error that may be introduced, generally unwittingly, into an investigation. Selection bias is due to systemic differences between those selected and not selected for a study. When selecting all admissions to a community hospital, alcoholics may be overrepresented among hospital patients and not reflect the community base from which the patients were admitted. Further, the investigator has not chosen a control sample but only patients already in the hospital, which further invalidates any outcome. While other biases may creep into this study, the selection bias is the major problem with the study.
Select the ONE best lettered answer that is most closely associated with it. Each lettered answer may be selected once, more than once, or not at all.Workers in certain occupations are exposed to diseases for which animals are the reservoir. These workers may then become a source of infection to others.Butchers are most likely to acquire and transmit the infectious disease?
Answer(s): A
Cutaneous anthrax is associated with a characteristic skin lesion, which becomes infected by the introduction of the bacillus through the skin. Occasionally, an infected carcass is not identified before butchering. A minor wound on the butcher may become infected. Human anthrax is secondary to the disease in animals, primarily mammals. In humans, the disease has three major clinical forms:cutaneous, inhalational, and GI.
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