MedStats Google Group

Re: {MEDSTATS} Re: sample size for sensitivity/specificity

m861h...@btinternet.com (Martin Holt) — Tue, 17 Nov 2009 17:52:02 UT

If I understand correctly, Evie will need to be able to have confidence intervals simultaneously for sensitivity and specificity. Googling, I found this (it comes with no guarantees). Beware the wrap-over.

[link]

Re: {MEDSTATS} Re: sample size for sensitivity/specificity

brown...@gmail.com (Barry Brown) — Tue, 17 Nov 2009 16:43:38 UT

I have written a program called CONFINT that calculates the sample size
necessary to
have a specified probability that the confidence interval length is not
longer than some
specified size. The program is free and includes Fprtran90 source, Win32
and Mac
executables. Download from
[link]

Estimating test retest and inter rater reliability

s.wh...@sgul.ac.uk (s.white@sgul.ac.uk) — Tue, 17 Nov 2009 12:44:07 UT

Dear All

Is it possible to obtain estimates of test retest reliability and
inter rater reliability using the following design?

Time 1 Time 2
S1 rated by R1 S1 rated by R1
S2 rated by R1 S2 rated by R2
S3 rated by R2 S3 rated by R2

Re: {MEDSTATS} Re: sample size for sensitivity/specificity

sos_st...@yahoo.co.uk (Evie) — Tue, 17 Nov 2009 11:12:22 UT

That's great, thank you all for your help.

Evie

Re: {MEDSTATS} Re: sample size for sensitivity/specificity

tfr...@gmail.com (Thomas Fröjd) — Tue, 17 Nov 2009 09:34:59 UT

Just for your information, if I remember it correctly there is a typo
in the graph suggested below in the pdf version. The correct graph can
be had at the BMJ website.

On 16 Nov, 19:27, Pedro Emmanuel Alvarenga Americano do Brasil

Re: {MEDSTATS} Re: Sample size for Repeated Measures

d.e.kornb...@herts.ac.uk (kornbrot) — Tue, 17 Nov 2009 07:54:43 UT

G*Power does this and more
[link]
diana

Professor Diana Kornbrot
email: d.e.kornb...@herts.ac.uk
web: [link]
Work
School of Psychology
University of Hertfordshire
College Lane, Hatfield, Hertfordshire AL10 9AB, UK

Re: {MEDSTATS} Re: Sample size for Repeated Measures

e.sabagh...@gmail.com (ehsan sabaghian) — Tue, 17 Nov 2009 05:50:31 UT

Thank you for your advice, but I have to analyze data via Repeated Measures
ANOVA method,
so I have to estimate sample size for this kind of test.

Re: {MEDSTATS} Re: Sample size for Repeated Measures

bwea...@lakeheadu.ca (Bruce Weaver) — Mon, 16 Nov 2009 23:09:42 UT

If I follow, you have one group that will be measured 5 times, and you
want to have power to detect a mean change (drop) of at least 2 points
from time 1 to time 5, or at least to one of the time points after
time 1. Is this right?

What type of analysis do you intend to do? Repeated measures ANOVA?

Re: Confidence interval for ratio of independent binomial proportions

tho...@gmx.de (Thomas Keller) — Mon, 16 Nov 2009 22:55:47 UT

John, we agree.

Therefore I gave the introductionary remark about the two worlds of
science/mathematics on the one hand and guidelines on the other hand.

From a former discussion in this forum I know, that you work on an
project which is due to HPV related FDA-guideline. But this guidelines

Re: Confidence interval for ratio of independent binomial proportions

brown...@gmail.com (Barry W Brown) — Mon, 16 Nov 2009 21:47:56 UT

Free Code for Clopper Pearson CI and requisite sample size

We provide two programs relevent to Clopper-Pearson confidence limits.
The first (BP1CI) calculates these intervals; the second (CONFINT)
calculates the sample size necessary to have a specified probability
that the length of the interval is not larger than a particular

Re: {MEDSTATS} Re: Sample size for Repeated Measures

e.sabagh...@gmail.com (ehsan sabaghian) — Mon, 16 Nov 2009 20:11:14 UT

I want to compare 5 mean in one group in a period of time that I said. In a
similar study with 3 time, they recorded 3 mean and standard deviation:

Time Mean SD
first 21.4 3
2nd 19.2 4.2
3rd 19.3 3.9

Now I want to do the same study with 5 time. The minimum effect is nearly

Re: {MEDSTATS} Re: Sample size for Repeated Measures

bwea...@lakeheadu.ca (Bruce Weaver) — Mon, 16 Nov 2009 18:49:14 UT

OK, good. Now what is the effect you want to have power to detect,
and what is the minimum effect size that would be considered
practically important?

--
Bruce Weaver
bwea...@lakeheadu.ca
[link]
"When all else fails, RTFM."

Re: {MEDSTATS} Re: Sample size for Repeated Measures

emmanuel.bra...@gmail.com (Pedro Emmanuel Alvarenga Americano do Brasil) — Mon, 16 Nov 2009 18:29:50 UT

Sorry... I posted a answer for another email with similar heading. Please
ignore it?
Abraço forte e que a força esteja com você,

Dr. Pedro Emmanuel A. A. do Brasil
Instituto de Pesquisa Clínica Evandro Chagas
Fundação Oswaldo Cruz
Rio de Janeiro - Brasil

2009/11/16 Pedro Emmanuel Alvarenga Americano do Brasil <

Re: {MEDSTATS} Re: sample size for sensitivity/specificity

emmanuel.bra...@gmail.com (Pedro Emmanuel Alvarenga Americano do Brasil) — Mon, 16 Nov 2009 18:27:40 UT

If you would like something very simple and straight I suggest this reading!

[link]

It implments a graph wich no formulars or computers is necessary. Very good
for starters.

Abraço forte e que a força esteja com você,

Dr. Pedro Emmanuel A. A. do Brasil

Re: Confidence interval for ratio of independent binomial proportions

jsueber...@gmail.com (John Uebersax) — Mon, 16 Nov 2009 16:25:12 UT

Thomas,

It's probably worth mentioning that the Clopper-Pearson intervals are
not exact in the modern sense (as in permutation-based methods).
George Cassella recommends the latter (permutation) exact approach in
his comment to:

Lawrence D. Brown, T. Tony Cai and Anirban DasGupta, Interval