help midas chiplotalso see: midas

Title

midas chiplot -- Chi-plot for bivariate association in diagnostic meta-analysis

Syntax

midas chiplot
tp fp fn tn
[if exp]
[in range]
[, options]

Styling
scatteropts(scatter_options) marker options for the scatter panel points

fitopts(line_options) options for the linear fit line in the scatter panel

chiopts(scatter_options) marker options for the chi-plot panel points

graph_options any twoway options passed to both panels

Description

midas chiplot produces a combined display of two panels. The left panel
is a scatter plot of logit(Se) against logit(Sp) with a linear fit line. The
right panel is the chi-plot: the chi-statistic (chi_i) plotted against
the lambda-statistic (lambda_i) for each study, with horizontal reference
lines at ±1.78/sqrt(n) marking the independence band.

The four variables must be supplied in the order tp fp fn tn. Logit
sensitivity and logit specificity are computed internally with a 0.5
continuity correction:

logit(Se) = logit[(tp + 0.5) / (tp + fn + 1)]

logit(Sp) = logit[(tn + 0.5) / (tn + fp + 1)]

Under independence the chi-statistics scatter randomly within the band.
Systematic departures indicate positive (chi > 0) or negative (chi < 0)
association. In diagnostic meta-analysis, negative values of chi concentrated
near high lambda indicate the SROC threshold effect: studies with high
sensitivity tend to have low specificity.

The Spearman rank correlation between logit(Se) and logit(Sp) is reported
in the chi-plot title.

Options

scatteropts(scatter_options) overrides the default style of
the scatter panel points (default: open circles, grey fill), e.g.
scatteropts(mcolor(navy) msymbol(circle)).

fitopts(line_options) overrides the default style of the
linear fit line in the scatter panel, e.g. fitopts(lcolor(maroon)).

chiopts(scatter_options) overrides the default style of the
chi-plot panel points (default: open squares, grey fill), e.g.
chiopts(mcolor(maroon) msymbol(square_hollow)).

Example

. use midas_example_data, clear

. midas chiplot tp fp fn tn

. midas chiplot tp fp fn tn, scatteropts(mcolor(navy)) chiopts(mcolor(maroon))

References

Fisher NI, Switzer P. Chi-plots for assessing dependence.
Biometrika 1985;72:253–265.
https://doi.org/10.1093/biomet/72.2.253

Fisher NI, Switzer P. Graphical assessment of dependence: is a picture
worth 100 tests? The American Statistician 2001;55:233–239.
https://doi.org/10.1198/000313001317098248

Also see

midas, midas bivbox