# [R] how to interpret the results of a simint call

Colm Connolly colmconn at gmail.com
Wed Apr 12 18:21:19 CEST 2006

```Hi all,

I've done some anovas, found some significance and proceeded to do the
post hoc tests to determine the source of the significance. I used the
multcmp package as suggested by Andy Liaw (thank you).

I am, however, unsure how to interpret the results of the call to
simint. Could someone help me with this?

I've attached the code and the results it produced. There are 3 groups
(ctrl,long,short) and I'm trying to see if the data in the Mean_12
column (in the example below) differs based on group membership.

for (meanCol in meanColumns) {
roi.err.aov<-aov(eval(parse(text=meanCol)) ~ Group, data=roi.errs);
HSD.err<-simint(eval(parse(text=meanCol)) ~ Group, data=roi.errs,
type="Tukey");
cat("################################################################################\n");
cat("### Summary of AOV for ", meanCol, " cluster: ", i, "\n");
print(summary(roi.err.aov))
print(summary(HSD.err))
i<-i+1;
}

################################################################################
### Summary of AOV for  Mean_12  cluster:  12
Df  Sum Sq Mean Sq F value   Pr(>F)
Group        2 6368494 3184247  8.8536 0.001627 **
Residuals   21 7552730  359654
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

Simultaneous 95% confidence intervals: Tukey contrasts

Call:
simint.formula(formula = eval(parse(text = meanCol)) ~ Group,
data = roi.stops, type = "Tukey")

Tukey contrasts for factor Group

Contrast matrix:
Groupctrl Grouplong Groupshort
Grouplong-Groupctrl  0        -1         1          0
Groupshort-Groupctrl 0        -1         0          1
Groupshort-Grouplong 0         0        -1          1

Absolute Error Tolerance:  0.001

95 % quantile:  2.519

Coefficients:
Estimate    2.5 %   97.5 % t value Std.Err. p raw p Bonf
Grouplong-Groupctrl  -134.246 -930.286  661.794  -0.425  316.076 0.675  1.000
Groupshort-Groupctrl  978.056  182.016 1774.097   3.094  316.076 0.005  0.016
Groupshort-Grouplong 1112.303  400.303 1824.303   3.934  282.707 0.001  0.002
Grouplong-Groupctrl  0.906
Groupshort-Groupctrl 0.015
Groupshort-Grouplong 0.002