parallelFisher {metapod} | R Documentation

## Combine parallel p-values with Fisher's method

### Description

Combine p-values from parallel tests with Fisher's method. Each group of p-values is defined from the corresponding entries across all vectors.

### Usage

    parallelFisher(p.values, log.p = FALSE)

### Arguments

`p.values` | A list of numeric vectors of the same length, containing the p-values to be combined.
`log.p` | Logical scalar indicating whether the p-values in `p.values` are log-transformed.

### Details

The joint null hypothesis for each group is that all of the individual null hypotheses are true. Fisher's method combines information from all individual nulls to determine if the joint null should be rejected. Compared to Stouffer's and Pearson's methods, Fisher's method provides more sensitivity to the smallest individual p-value. This method is only applicable to independent tests and no weights are considered.

The representative test for each group is defined as the test with the lowest p-value, as this has the greatest effect on the combined p-value. All tests for each group are considered to be influential as increasing any of them (e.g., to unity) would result in a larger combined p-value.

### Value

A list containing:

- `p.value`, a numeric vector of length equal to the length of each vector in `p.values`. This contains the combined Fisher p-value for each group, log-transformed if `log.p=TRUE`.

- `representative`, an integer scalar specifying the representative test in each group. Specifically, this refers to the index of the vector of `p.values` containing the representative test.

- `influential`, a list of logical vectors mirroring the structure of `p.values`. Entries are `TRUE` for any p-value that is deemed “influential” to the final combined p-value.

### Author(s)

Aaron Lun

### References

Fisher RA (1925). Statistical Methods for Research Workers. Oliver and Boyd (Edinburgh).

### See Also

`groupedFisher`, for a version that combines p-values based on a grouping factor.

`parallelStouffer` and `parallelPearson`, for different approaches to testing a joint null of independent hypotheses.

### Examples

    p1 <- rbeta(100, 0.8, 1)
    p2 <- runif(100)
    p3 <- rbeta(100, 0.5, 1)

    # Standard application:
    out <- parallelFisher(list(p1, p2, p3))
    str(out)

    # With log p-values.
    out <- parallelFisher(list(log(p1), log(p2), log(p3)), log.p=TRUE)
    str(out)

[Package metapod version 1.0.0 Index]