Bug 17345 - power.prop.test() function displays proportions over 1
Summary: power.prop.test() function displays proportions over 1
Alias: None
Product: R
Classification: Unclassified
Component: Analyses (show other bugs)
Version: R 3.4.1
Hardware: Other Other
: P5 enhancement
Assignee: R-core
Depends on:
Reported: 2017-09-27 14:45 UTC by gael.millot
Modified: 2017-09-27 14:45 UTC (History)
0 users

See Also:


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Description gael.millot 2017-09-27 14:45:04 UTC

Since the modification of the power.prop.test() function in R 3.1.3
("power.t.test() and power.prop.test() now make use of the extendInt option of uniroot() and hence work in more extreme cases. (PR#15792)")
the function can display proportion over 1 without warning message.

power.prop.test(n=30, p1=0.90, p2=NULL, sig.level=0.05, power=0.8, alternative="two.sided", strict=TRUE)

     Two-sample comparison of proportions power calculation 

              n = 30
             p1 = 0.9
             p2 = 1.030182
      sig.level = 0.05
          power = 0.8
    alternative = two.sided

NOTE: n is number in *each* group

This was not the case before the modification.

Moreover, in ?power.prop.test(), the following sentence is not clear:

"If one of them is computed p1 < p2 will hold, although this is not enforced when both are specified".

Many thanks for your help.