one sample t test (with two different intervention to the same patients)

[Manoj Diwakar]

Dear Biostatistics Team,

i request to discuss an objective that 

     Obj-  mean value of intervention one is better than the other mean value  intervention two to the same subjects.

should I go for one sample t test (one sided ) or  ??

sample 1 (Same subject) -

Sample 2 (same subject) -

With regard, 

Manoj Kumar, PhD Post-Doctoral Associate ( in the area of Data Science, Biostatistics, Health Economics) 

McGowan Institute for Regenerative Medicine University of Pittsburgh, Pittsburgh, Pennsylvania USA Email id: MAK...@pitt.edu Mobile no +14125898944 WhatsApp no: +91-9990346151

Best Regards,

Dr. Manoj Kumar Diwakar, M.Sc., M.Phil.,Ph.D. (Statistics)
Assistant Professor
Centre for Economic Studies & Planning (CESP), School of Social Sciences (SSS-II),
Jawaharlal Nehru University, New Delhi-110067, India. 

Email id: Manojdiw...@gmail.com  & mobile-09990346151

Area of Specialisation: Statistics, Econometric and Applied Mathematics 

Research Methodology -Quantitative Methods, Health Economics, Clinical Trial-Biostatistics

Data analysis and Software: SAS, SPSS, R, STATA, SPSS AMOS

[Scott Millis]

Paired t test or Wilcoxon signed rank test?
 

Scott Millis 

Sent telepathically

On Sep 20, 2023, at 4:00 PM, Manoj Diwakar <manojdiw...@gmail.com> wrote:



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[Rich Ulrich]

It looks to me like two factors, Intervention and Order ("First, or Second?"),

in a Repeated Measures design.  Googling "Crossover design" might lead to

a description of concerns for testing the interaction and parallel correlations.  

By the way, having a Pre score as a covariate might be informative.

Rich Ulrich

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From: meds...@googlegroups.com <meds...@googlegroups.com> on behalf of Manoj Diwakar <manojdiw...@gmail.com>
Sent: Wednesday, September 20, 2023 4:00 PM
To: meds...@googlegroups.com <meds...@googlegroups.com>
Subject: {MEDSTATS} one sample t test (with two different intervention to the same patients)

 

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[Manoj Diwakar]

But here my objections is to look the intervention (treatment 1) > interventions (treatment 2)

It should go for one sided t test … 

Thanks and Regards
Dr.Manoj Kumar Diwakar
Assistant Professor
Jawaharlal Nehru University
JNU, New Delhi, India
+91-9990346151
i touch

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[Rich Ulrich]

It would be unconventional, but not improper, to use compute the

Repeated Measures analysis as I described, and essentially achieve

a one-tailed, paired t-test by dividing the observed p-value by two.

You have not described the Treatments or the measurements or the

logic of the experiment, so, maybe you do have reason to ignore Order

and reason to use a one-tailed (paired t) test.

I hope that you recognize that using a one-tailed test in an experiment 

is also unconventional. Some journal editors and reviewers are more

opposed than others. One criterion that I have suggested to consultees:  

Would it be totally uninteresting and not worth reporting if the result were

significant in the wrong direction?  - For some experimental Treatments,

that might be the case, but that still leaves you with reader prejudice.

You will avoid criticism and complaint if you increase your sample by a 

bit to achieve the same power for a two-tailed test. My memory of

applying a one-tailed test in clinical research is, I did it ONCE:  It was for

testing an ancillary, a-priori hypothesis, which we wrote up in the grant

proposal.  It was to be performed on a subsample in a larger (expensive)

study, so there was no realistic chance of increasing the N; and "one-tailed"

was specified in order to achieve a half-decent power (60% or 70%). The

journal accepted it because the grant proposal proved we were not making

up the argument after the fact.

Rich Ulrich

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From: meds...@googlegroups.com <meds...@googlegroups.com> on behalf of Manoj Diwakar <manojdiw...@gmail.com>

Sent: Wednesday, September 20, 2023 5:23 PM
To: meds...@googlegroups.com <meds...@googlegroups.com>
Subject: Re: {MEDSTATS} one sample t test (with two different intervention to the same patients)

 

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