What is between study variance?
Between-study variance refers to variation across study findings beyond random sampling error, and its quantification is often of interest and aids in the interpretation of results of a meta-analysis.
How is study variance calculated?
The study variation is calculated as the standard deviation for each source of variation multiplied by 6 or the multiplier that you specify in Study variation. Usually, process variation is defined as 6s, where s is the standard deviation as an estimate of the population standard deviation (denoted by σ or sigma).
What is prespecified secondary analysis?
The primary analyses are pre-specified in the protocol and the findings form the basis for recommendations and clinical decisions. They typically adhere to the intention-to-treat principle. Secondary analyses are supplemental and of various sorts. Although some may be pre-specified, many are not.
How does variance affect confidence interval?
A larger sample size or lower variability will result in a tighter confidence interval with a smaller margin of error. A smaller sample size or a higher variability will result in a wider confidence interval with a larger margin of error. The level of confidence also affects the interval width.
What is a good confidence interval?
The answer: In general, narrow confidence intervals are more desirable since this provides us with a narrow range of values that we’re confident contains some population parameter….Example: Calculating a Confidence Interval.
| Confidence Level | z-value |
|---|---|
| 0.90 | 1.645 |
| 0.95 | 1.96 |
| 0.99 | 2.58 |
What is DerSimonian and Laird?
A variation on the inverse-variance method is to incorporate an assumption that the different studies are estimating different, yet related, intervention effects. This produces a random-effects meta-analysis, and the simplest version is known as the DerSimonian and Laird method (DerSimonian 1986).
What is prespecified analysis?
A prespecified subgroup analysis is one that is planned and documented before any examination of the data, preferably in the study protocol. This analysis includes specification of the end point, the baseline characteristic, and the statistical method used to test for an interaction.
What is difference between primary and secondary endpoint?
The primary endpoint of a clinical trial is the endpoint for which the trial is powered. Secondary endpoints are additional endpoints, preferably also pre-specified, for which the trial may not be powered.
What does high variance mean?
A high variance indicates that the data points are very spread out from the mean, and from one another. Variance is the average of the squared distances from each point to the mean. The process of finding the variance is very similar to finding the MAD, mean absolute deviation.