# Online odds ratio calculator

Use this calculator to determine a confidence interval for your odds ratio. An odds ratio is a measure of association between the presence or absence of two. Online calculator to calculate odds ratio confidence interval for 2x2 contingency table. Odds Ratio Calculator Formula: r = (p1 * (1 - p2)) / (p2 * (1 - p1)); Where: p1: The probability of event in the experimental group p2: The probability of event in the. Specifically, it tells you how the presence or absence of property A has an effect on the presence or absence of property B. Then all one needsto do to construct confidence intervals about the natural logarithm is to calculate the standard error using the above formula and add that value or a multiple of that value to the log of the odds ratio value for the upper CI confidence interval and subtract that value or a multiple of that value to the log of the odds ratio value for the lower CI. This table should have been changed because an OR value of 0. The OR is different. The value of the odds ratio tells you how much more likely someone under 25 might be to make a claim, for example, and the associated confidence interval indicates the degree of uncertainty associated with that ratio. The odds ratio is simply the ratio between the following two ratios: All that can be said is that the women who had an initial needle biopsy had fewer surgeries than women who did not have the biopsy. The contingency table summarises the outcomes of each individual sampled in terms of whether Properties A and B are absent or present. Sheskin DJ Handbook of parametric and nonparametric statistical procedures. There are a number of statistics that are helpful for making decisions about clinical interventions or drawing conclusions about effects of various substances or events in health-related situations, and one seen frequently is called the odds ratio. You are welcome to keep this page and use the calculator off-line. The odds ratio can be compared with the Risk Ratio.