<p>Determining sample size for an animal experiment is no different than in research with human subjects. What you need to know is the effect size, the significance level and the power (which is the probability that the test detects a significant effect assuming that there is one). The tricky part is getting the effect size (for an interesting discussion have a look at <a href="https://cogsci.stackexchange.com/questions/3384/how-to-estimate-an-expected-effect-size-for-a-planned-psychology-study">this thread</a>). The other two things are chosen by you as the experimenter. An overview paper on power analysis was written by Cohen (1992).</p>

<p>References</p>

<p>Cohen, J. (1992). A power primer. <em>Psychological Bulletin</em>, 112(1), 155. <a href="http://classes.deonandan.com/hss4303/2010/cohen%201992%20sample%20size.pdf" rel="nofollow noreferrer">PDF</a></p>

CC BY-SA 3.0
2013-07-15T20:59:42.397Z
2013-07-16T07:48:05.150Z
2017-04-13T12:56:16.467Z
Jens Kouros
<p>In human research, we define our universe and estimate the effect size we expect to observe, then we can draw the a sample of a given size.</p>

<p>How is sample size determined for experiments in the animal research field?</p>

CC BY-SA 3.0
2013-07-15T19:10:02.087Z
Do you mean 'determine the sample size', not 'draw/estimate the sample size'? Is this question in the context of power analysis?
Pavel
CC BY-SA 3.0
2013-07-16T03:23:57.820Z
@Pavel I tweaked the question in line with what you are expecting.
Jeromy Anglim
CC BY-SA 3.0
2013-07-16T06:58:08.643Z
Truth is, for many experiments, whether with animals or humans, people don't estimate an effect size or conduct power analysis at all.
Gala
<statistics><animal-cognition><sampling>
How is sample size determined in animal research?
Henrique Gomide
# How is sample size determined in animal research?

(Asked by: username_0 on 2013-07-15)

In human research, we define our universe and estimate the effect size we expect to observe, then we can draw the a sample of a given size.

How is sample size determined for experiments in the animal research field?

**Tags:** statistics, animal-cognition, sampling

> **Comments:**
> **username_1**: Do you mean 'determine the sample size', not 'draw/estimate the sample size'? Is this question in the context of power analysis?  
> **username_2**: @username_1 I tweaked the question in line with what you are expecting.  
> **username_3**: Truth is, for many experiments, whether with animals or humans, people don't estimate an effect size or conduct power analysis at all.  

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## 1 answers

### Answer by username_4 on 2013-07-15. Score: 6

Determining sample size for an animal experiment is no different than in research with human subjects. What you need to know is the effect size, the significance level and the power (which is the probability that the test detects a significant effect assuming that there is one). The tricky part is getting the effect size (for an interesting discussion have a look at [this thread](https://cogsci.stackexchange.com/questions/3384/how-to-estimate-an-expected-effect-size-for-a-planned-psychology-study)). The other two things are chosen by you as the experimenter. An overview paper on power analysis was written by Cohen (1992).

References

Cohen, J. (1992). A power primer. *Psychological Bulletin*, 112(1), 155. [PDF](http://classes.deonandan.com/hss4303/2010/cohen%201992%20sample%20size.pdf)


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