.- help for ^pwploti^ .-Plot Power curve for sample size and power calculation ------------------------------------------------------ ^pwploti^ #1^,^ ^d^list^(^#^)^ [ ^nf^rom^(^#^)^ ^nt^o^(^#^)^ ^i^nc^(^#^)^ ^l^ist ^key^() ^b1()^ ^b2()^ sampsi_options graph_options ]

Description ----------- ^pwploti^ plots statistical power on the Y-axis and the required sample size of on the X-axis. Several lines can be plotted on the power curve, each one corresponding to a value of difference (defined in ^dlist^) between two groups.

It is an extension to @sampsi@. Most @sampsi@ options are accepted. Note: ^pwploti^ only specifies the mean or proportion value in group 1, #1. The corresponding values in group 2 are derived from the #1 and differences between two groups, ^d^list. -keyplot- should be installed when more than four labels are needed.

Options specific to ^pwploti^ --------------------------- ^d^list lists possible differences between two groups. ^nf^rom^(^#^)^ and ^nt^o^(^#^)^ assign the range sample size with ^i^nc^(^#^)^ increment. ^l^ist gives detail values of calculated statistical powers. ^key^ gives a list of strings as a legend to keyplot. See -keyplot- ^b1^ and ^b2^give different titles at the bottom

See ^sampsi^ for details

Examples --------- 1. Plot of Two-sample comparison of mean1 to mean2 (different possible values) . ^pwploti 132, dlist(8,10, 15,20) nfrom(10) nto(100) i(5) sd1(15) sd2(18)^ 2. One-sample comparison of mean to hypothesized value = 180. . ^pwploti 180, dlist(8,10, 15,20) nfrom(10) nto(100) i(5) sd(46) onesam^ 3. One-sample comparison of mean to hypothesized value = 0. . ^pwploti 0, dlist(1,2,3) nfrom(10) nto(100) i(5) sd(4) n(25) onesam^

4. Two-sample comparison of proportions. . ^pwploti .5, dlist(-.1,-.2,-.3) nfrom(10) nto(100) i(5) xlab(10(10)100)^

5. One-sample comparison of proportion to hypothesized value = 0.5: . ^pwploti 0.3, dlist(.1,.15,.2,.25,.3) nfrom(10) nto(100) i(5) onesam^

6. Two-sample comparison of proportions with a legend for the differences . ^pwploti .5, dlist(-.1,-.2,-.3 .-5 .-10) nfrom(10) nto(100) i(5) xlab(10(10 > )100)^ ^key(-.1 -.2 -.3 -.5 -.10)

4. Two-sample comparison of proportions with different titles. . ^pwploti .5, dlist(-.1,-.2,-.3) nfrom(10) nto(100) i(5) xlab(10(10)100)^ ^b1("Sample size (N)") b2("Power to detect (alpha 0.05)")^

Author ------ Zhiqiang Wang Menzies School of Health Research Darwin, Australia email: wang@@menzies.su.edu.au Modified by Jan Brogger, University of Bergen, Norway 04dec2000, email: jan.brogger@med.uib.no

Also see -------- Manual: [R] sampsi On-line: help for @sampsi@, @immed@