Contents
What is a stratified risk ratio?
Stratification means making a separate table of disease by exposure for each possible confounder combination. If the odds ratio or risk ratios for strata in a series of stratified tables for the tests are not similar, then interaction between the stratifying factor and the risk factor are present.
What if the odds ratio is not significant?
If an odds ratio (OR) is 1, it means there is no association between the exposure and outcome. So, if the 95% confidence interval for an OR includes 1, it means the results are not statistically significant. Sorry, this is not statistically significant.
How does stratified analysis control for confounding?
Stratification allows to control for confounding by creating two or more categories or subgroups in which the confounding variable either does not vary or does not vary very much.
What is the difference between odds and odds ratio?
Odds are the probability of an event occurring divided by the probability of the event not occurring. An odds ratio is the odds of the event in one group, for example, those exposed to a drug, divided by the odds in another group not exposed.
How is a risk ratio calculated in a stratified analysis?
Using the notation in this table estimates for a risk ratio or an odds ratio would be computed as follows: To explore and adjust for confounding, we can use a stratified analysis in which we set up a series of two-by-two tables, one for each stratum (category) of the confounding variable.
How is the odds ratio used to determine risk?
The odds ratio can also be used to determine whether a particular exposure is a risk factor for a particular outcome, and to compare the magnitude of various risk factors for that outcome. OR=1 Exposure does not affect odds of outcome
How much confidence is there in a weighted odds ratio?
If the weighted odds ratio or risk ratio (not for case-control studies) has confidence limits that do not include 1.0, there is a statistical association with 95% confidence between the disease and the exposure without confounding by the stratifying factor.
How to adjust for confounding in a stratified analysis?
To explore and adjust for confounding, we can use a stratified analysis in which we set up a series of two-by-two tables, one for each stratum (category) of the confounding variable. Having done that, we can compute a weighted average of the estimates of the risk ratios or odds ratios across the strata.