bayesmeta (version 3.4)

Cochran1954: Fly counts example data

Description

This data set gives average estimated counts of flies along with standard errors from 7 different observers.

Usage

data("Cochran1954")

Format

The data frame contains the following columns:

observer	character	identifier
mean	numeric	mean count
se2	numeric	squared standard error

Details

Quoting from Cochran (1954), example 3, p.119: “In studies by the U.S. Public Health Service of observers' abilities to count the number of flies which settle momentarily on a grill, each of 7 observers was shown, for a brief period, grills with known numbers of flies impaled on them and asked to estimate the numbers. For a given grill, each observer made 5 independent estimates. The data in table 9 are for a grill which actually contained 161 flies. Estimated variances are based on 4 degrees of freedom each. [...] The only point of interest in estimating the overall mean is to test whether there is any consistent bias among observers in estimating the 161 flies on the grill. Although inspection of table 9 suggests no such bias, the data will serve to illustrate the application of partial weighting.”

Examples

data("Cochran1954")
if (FALSE) {
# analysis using improper uniform prior
# (may take a few seconds to compute!):
bma <- bayesmeta(y=Cochran1954[,"mean"], sigma=sqrt(Cochran1954[,"se2"]),
                 label=Cochran1954[,"observer"])

# show joint posterior density:
plot(bma, which=2, main="Cochran example")
# show (known) true parameter value:
abline(h=161)

# show forest plot:
forestplot(bma, zero=161)
}