How do you find the sample size for a matched case-control study?
The sample size for a 1:1 matched study is the number of discordant pairs required (calculated from the desired power for a specified odds ratio and a given level of statistical significance) divided by the estimated probability that a randomly selected pair is discordant (calculated from the average prevalence of …
How do you calculate the power of a case-control study?
Power calculations are derived for matched case-control studies in terms of the probability po of exposure among the control patients, the correlation coefficient phi for exposure between matched case and control patients, and the odds ratio psi for exposure in case and control patients.
What type of sampling is used in case-control studies?
Case-base sampling (also known as “case-cohort” sampling): Controls are selected from the population at risk at the beginning of the follow-up period in the cohort study within which the case-control study was nested.
What is the ideal ratio of cases to controls for a case-control study?
Investigators planning case-control studies are usual- ly advised to include no more than four or five controls per case because little statistical power is gained by fur- ther increasing this ratio (1,2).
What is the difference between matched and unmatched case-control study?
Abstract. Multiple control groups in case-control studies are used to control for different sources of confounding. For example, cases can be contrasted with matched controls to adjust for multiple genetic or unknown lifestyle factors and simultaneously contrasted with an unmatched population-based control group.
What is the difference between matched and unmatched case control study?
What are the advantages of case-control studies?
Advantages: They are efficient for rare diseases or diseases with a long latency period between exposure and disease manifestation. They are less costly and less time-consuming; they are advantageous when exposure data is expensive or hard to obtain.
What is difference between Case control and cohort study?
Whereas the cohort study is concerned with frequency of disease in exposed and non-exposed individuals, the case-control study is concerned with the frequency and amount of exposure in subjects with a specific disease (cases) and people without the disease (controls).
How do you select cases in a case-control study?
Selection of the Controls
- The comparison group (“controls”) should be representative of the source population that produced the cases.
- The “controls” must be sampled in a way that is independent of the exposure, meaning that their selection should not be more (or less) likely if they have the exposure of interest.
Why is matching used in case-control studies?
Matched case-control study designs are commonly implemented in the field of public health. While matching is intended to eliminate confounding, the main potential benefit of matching in case-control studies is a gain in efficiency.