Question
Asked 23rd Jun, 2014

# How can I calculate the sample size in an animal trial?

How can I calculate the sample size for an animal trial? How many animals per group would be statistically significant for generalization of the results?

## Most recent answer

16th Oct, 2021
Shamim Molla
Square Pharmaceuticals Ltd.
Really it was a very important question and answer from the researchers was so good. I have learned many from this question answer session. Thank you Dear honourable sir.

## Popular answers (1)

28th Jan, 2016
Muayyad Ahmad
University of Jordan
Hi, regardless the element of the sample if they are files, records, animals, lab resutls or people, the sample size is calculated similarly.
To do power analysis to estimate your sample size, you have to write your hypothesis, and based on that you decide what statistical test you will use. It should be one of the inferential statistics. so you need to determine the following: alpha {standard to be .05}, power [standard to be .80], effect size {small, moderate, or large, each test has its own value, you can find these values in the net}. Then download free programs to calculate the sample size such as G. power.
9 Recommendations

## All Answers (22)

23rd Jun, 2014
Shahinaz A. Elsherif
Ain Shams University
How to calculate sample size in animal studies?
23rd Jun, 2014
Shahinaz A. Elsherif
Ain Shams University
That's very helpful. I will be studying histological measures so i guess 3-5 will be enough per group. Thank you for your time.
23rd Jun, 2014
Nikola M Stojanovic
University of Niš
Yes I think for histological measures 3-5 animals are sufficient but to be sure any way use 5 if you can (at least in experimental groups)
1 Recommendation
16th Jul, 2014
M. Ricky Ramadhian
Lampung University
how about the statistical method for anima sample?can i get it?
27th Jul, 2014
Viola Galligioni
Trinity College Dublin
Hi Shahinaz,
as mentioned before there are several factors affecting the number of your sample. FIrst you should decide the sample unit (one animal, one cage etc) and according to the statystical analysis you want to perform, you carry out the power analysis (to get the n°of sample). One really nice website to understand these key-points is http://www.3rs-reduction.co.uk/ from Prof Festing.
Hope it helps, good luck!
Viola
2 Recommendations
5th Aug, 2014
Shahinaz A. Elsherif
Ain Shams University
Thank you very much Viola
5th Jan, 2015
Shahinaz A. Elsherif
Ain Shams University
hi, i came across this very helpful website.
5 Recommendations
Please take the statistical method into considereation
1 Recommendation
28th Jan, 2016
Muayyad Ahmad
University of Jordan
Hi, regardless the element of the sample if they are files, records, animals, lab resutls or people, the sample size is calculated similarly.
To do power analysis to estimate your sample size, you have to write your hypothesis, and based on that you decide what statistical test you will use. It should be one of the inferential statistics. so you need to determine the following: alpha {standard to be .05}, power [standard to be .80], effect size {small, moderate, or large, each test has its own value, you can find these values in the net}. Then download free programs to calculate the sample size such as G. power.
9 Recommendations
24th Aug, 2016
Fu Shun Wong
University of Malaya
Hi Elena,
I find the information you provided is very useful? May I know the source of your information? I would like to know more about the justification of sample size.
4th Sep, 2016
Hossam Arafa
Pharmacy College,MTI
Usually we have two ways for calculating sample size; one robust power analysis that depends on a host of variables such as type one error (Alpha), effect size, SD, power effect and direction of effect (one-tailed VS two-tailed analysis)- the second method which is more easy but less accurate; the calculation of the E Value; E = Total number of animals − Total number of groups- E between 10 and 20 is acceptable. Despite its simplicity, one could argue that the calculated E value- though being in between 10 and 20, it may suggest low sample size that may lead to missing significant effects even if it exists in population. But to be honest, calculating sample size using the power analysis method needs a professional statistician.
2 Recommendations
22nd Dec, 2017
Amaresh Kumar Singh
Indian Institute of Technology Kanpur
Please guide....
How to calculate animal size and do power calculation for qualitative data (IHC data) ? Please suggest at your earliest. I am not able to justify animal number for my proposal. My whole study is based on only qualitative data (expression of molecular markers on tissue section).
22nd Dec, 2017
Amaresh Kumar Singh
Indian Institute of Technology Kanpur
Dear Dr. Elena Redondo Castro and Nikola M Stojanovic,
How did you reached to the conclusion that 3-4 or 5 animals will be suitable and appropriate for histological measures. Is there any calculation for it? I need to submit a grant in which reviewers asked for power calculation for the same.
please suggest...
1 Recommendation
2nd Feb, 2018
Debarshi Sarkar
Central University of Punjab
Yes! 5 animals are sufficient for histology and/or IHC. Among 5 animals depending on the sections you can choose minimum 10 non serial sections from each animal i.e. minimum 50 sections from each group (if the group is consist of 5 animals). To choose non serial sections you will have to consider sections which are minimum 30-50 micrometer apart. If you still feel problem then let me know.
1 Recommendation
5th Feb, 2018
Amaresh Kumar Singh
Indian Institute of Technology Kanpur
Dear Dr. Sarkar this calculation is done by statistical method. You may refer G-power softwar.
3 Recommendations
23rd Apr, 2021
Victoria Chinenye Obinna
University of Port Harcourt
Please refer to these papers, they contain the answers you seek:
1.) Arifin WN, Zahiruddin WM (2017) Sample size calculation in animal studies using resource equation approach. Malays J Med Sci 24(5):101–105 https:// doi.org/10.21315/mjms2017.24.5.11
2.) Charan J, Kantharia ND (2013) How to calculate sample size in animal studies? J Pharmacol Pharmacother 4:303–306
2 Recommendations
7th Jul, 2021
Rebecca Jo Ingram
Queen's University Belfast
2 Recommendations
11th Sep, 2021
Muhammad Torequl Islam
Bangabandhu Sheikh Mujibur Rahman Science and Technology University
Very good question and answers by the experts. I appreciate all of your efforts on this important issue.
1 Recommendation
18th Sep, 2021
Paulo Michel Pinheiro Ferreira
Universidade Federal do Piauí
Dear Rebecca Jo Ingram what fill out in white cells (group 1 / 2): number of animals or results expected (as tumor mass, for example)? Thanks ...
1 Recommendation
29th Sep, 2021
Ahmed Mead
Ondokuz Mayıs Üniversitesi
Really this is a very important question and we look forward to much more detailed answers.
1 Recommendation
16th Oct, 2021
Shamim Molla
Square Pharmaceuticals Ltd.
Really it was a very important question and answer from the researchers was so good. I have learned many from this question answer session. Thank you Dear honourable sir.

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