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From |
Nikolaos Pandis <npandis@yahoo.com> |

To |
"statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu> |

Subject |
Re: st: RE: RE: generate graph (try 2) |

Date |
Thu, 3 Nov 2011 03:51:28 -0700 (PDT) |

Dear Phil, The first piece of code worked well, the second had a minor issue on the twoway part probably from copy/paste etc-I fixed it no problem On a more careful reading of the code, although the graphs have a similar look to what want, I am wondering if this is not the graph I need. On the x-axis I would like to show the p-value and how the p-value decreases for a given effect/sd (effect/sd remain constant) as we increase the sample size. The idea is to show how interpreting trial results from p-values may be misleading as you may have an uniportant clinical effect which may be statistically significant or nonsignificant depending on the sample size used. If I unerstood correctly the code you supplied indicates how the sample size requirements decrease as the a-level changes? Please advise. Many thanks, Nick ----- Original Message ----- From: Philip Ryan <philip.ryan@adelaide.edu.au> To: statalist@hsphsun2.harvard.edu Cc: Sent: Thursday, November 3, 2011 9:48 AM Subject: st: RE: RE: generate graph (try 2) <<>> For reasons not clear to me, the return from my own initial posting seemed to have left out some carriage returns that were present in what I sent. Perhaps this, inserting several double carriage returns, will be better. (Of course, code should be run from the do file editor). *==== begin code ====* clear tempname temp_ss local sd .75 local pow 0.8 local m1 0.35 local m2 0 quietly { postfile `temp_ss' sample_size alpha using my_ss, replace forvalues alpha = .01(.01).2{ sampsi `m1' `m2', alpha(`alpha') power(`pow') sd(`sd') r(1) post `temp_ss' (r(N_1)) (`alpha') } postclose `temp_ss' } /* now make use of our new data set */ use my_ss list, clean abbrev(16) graph twoway line sample_size alpha, /// ytitle("sample size in each group") xlabel(0(.01).2) /// lwidth(medthick) lcolor(blue) *=== end code === Philip Ryan Professor and Director Data Management & Analysis Centre School of Population Health & Clinical Practice University of Adelaide Postal address: DMAC Mail Drop DX650 511 University of Adelaide 5005 South Australia Australia location: Level 6 Bice Building Royal Adelaide Hospital North Terrace Adelaide SA tel: +61 (0)8 83033570 fax: +61 (0)8 82234075 -----Original Message----- From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Philip Ryan Sent: Thursday, 3 November 2011 6:04 PM To: statalist@hsphsun2.harvard.edu Subject: st: RE: generate graph <<>> Something like this (grafting onto -sampsi-) ?: *==== begin code ====* clear tempname temp_ss local sd .75 local pow 0.8 local m1 0.35 local m2 0 quietly { postfile `temp_ss' sample_size alpha using my_ss, replace forvalues alpha = .01(.01).2{ sampsi `m1' `m2', alpha(`alpha') power(`pow') sd(`sd') r(1) post `temp_ss' (r(N_1)) (`alpha') } postclose `temp_ss' } /* now make use of our new data set */ use my_ss list, clean abbrev(16) graph twoway line sample_size alpha, /// ytitle("sample size in each group") xlabel(0(.01).2) /// lwidth(medthick) lcolor(blue) *=== end code === Philip Ryan -----Original Message----- From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Nikolaos Pandis Sent: Thursday, 3 November 2011 5:34 PM To: statalist@hsphsun2.harvard.edu Subject: st: generate graph Hi to all. I was wondering if someone could help me generate the following graph: twoway line graph showing on the y-axis: sample size and on the x-axis: p-value. The objective is to show how the p-value decreases (increases) as the sample size increases (decreases) given the same effect size and sd Many thanks, Nick * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**RE: st: RE: RE: generate graph (try 2)***From:*"Philip Ryan" <philip.ryan@adelaide.edu.au>

**References**:**st: generate graph***From:*Nikolaos Pandis <npandis@yahoo.com>

**st: RE: RE: generate graph (try 2)***From:*"Philip Ryan" <philip.ryan@adelaide.edu.au>

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