diag.evppi: Diagnostic Plots For The Results Of The EVPPI

In BCEA: Bayesian Cost Effectiveness Analysis

Diagnostic Plots For The Results Of The EVPPI

Description

The function produces either a residual plot comparing the fitted values from the INLA-SPDE Gaussian Process regression to the residuals. This is a scatter plot of residuals on the y axis and fitted values (estimated responses) on the x axis. The plot is used to detect non-linearity, unequal error variances, and outliers. A well-behaved residual plot supporting the appropriateness of the simple linear regression model has the following characteristics:

1. The residuals bounce randomly around the 0 line. This suggests that the assumption that the relationship is linear is reasonable.

2. The residuals roughly form a horizontal band around the 0 line. This suggests that the variances of the error terms are equal.

3. None of the residual stands out from the basic random pattern of residuals. This suggests that there are no outliers.

Usage

diag.evppi(evppi, he, plot_type = c("residuals", "qqplot"), interv = 1)

Arguments

evppi	A evppi object obtained by running the function evppi on a bcea model.
he	A bcea object containing the results of the Bayesian modelling and the economic evaluation.
plot_type	The type of diagnostics to be performed. It can be the 'residual plot' (residuals) or the Q-Q (quantile-quantile) plot (qqplot).
interv	Specifies the interventions for which diagnostic tests should be performed (if there are many options being compared)

Details

The second possible diagnostic is the Q-Q plot for the fitted value. This is a graphical method for comparing the fitted values distributions with the assumed underlying normal distribution by plotting their quantiles against each other. First, the set of intervals for the quantiles is chosen. A point (x,y) on the plot corresponds to one of the quantiles of the second distribution (y-coordinate) plotted against the same quantile of the first distribution (x-coordinate). If the two distributions being compared are identical, the Q-Q plot follows the 45 degrees line.

Value

Plot

Author(s)

Gianluca Baio, Anna Heath

References

\insertRef

Baio2011BCEA

\insertRef

Baio2013BCEA

See Also

bcea(), evppi()

BCEA documentation built on June 22, 2024, 11:08 a.m.