Hi Med,

I don't know if I have understood you properly, so I will answer that the "experimental unit" or the replicate is the sample you have each day. You have to consider at least 3 fields (you can go for more) at the CASA and count at leas 200 sperm, that would be considered a replicate for a treatment. Always check the concentration and adjust it to 50 mill sperm/ml aprox. to avoid any concentration artifact (the more concentrated the higher the velocities and vice versa-->dilution effect). I hope I have addressed all your concerns. Good luck,

Bea

Hi Bea 

Thank you for your interest 

I will explain a little more my problem

I tested the effect of serum taken from cows of different stages of the sexual cycle on the parameters of sperm motility (coincubation: Serum + sperm)

I am at the stage of statistical analysis.

to compare, for example, the effects of different sera on the VSL, I opted for an Anova taking as factor the day of the cycle.

as sperm count (total and motile) differs from one group to another, and groups are unequal variances (Levene test) and I even doubt on the normality of the parameter (the conditions to opt for an ANOVA are not met), I asked if I can take the field as experimental unit (instead of sperm) to work around this problem

Hi Med,

you don't need the sperm count to be equal,as  you don't usually have the exact sperm number in each replicate. In addition, your data do not necesarily need to be normal, but if you want to try, you could convert them properly (suqre root, log....) and see if you reach the normality running a Levene or any other test of your choice. What  I'd really suggest is to use a non-parametric test such us Mann-Whittney U test and not worry about the distribution. I hope this helped!!

Bea

Hi, this review may be helpful:

Statistical Series: Opportunities and challenges of sperm motility subpopulation analysis. Martínez-Pastor F, Tizado EJ, Garde JJ, Anel L, de Paz P. Theriogenology. 2011 Mar 15;75(5):783-95.

http://www.theriojournal.com/article/S0093-691X%2810%2900627-8/abstract

Hi Med

As I  understood your experimental design is to investigate the effect of different sera from different animals during different stages of the estrous cycle on sperm motility?

Is it the sperm samples different or the same sample?

And you are going to compare between different estrus cycle serum's effect on sperm motility, right?

If like that non-parametric statistical analysis will be your choice, whatever you use field or sperm as the experimental unit.

Best of luck

Dear colleague, definitely you need to choice non-parametric statistics as Ali said.

However, the sperm is not an experimental unit if motility is analyzed, as this is the result of a set of data provided by the group of sperm analyzed.

I wish it helps!

Hi,

If you are using CASA, in order to publish reproduce-able data, I consider you to check the WHO Guideline on how to define the concentration.

In Manchester Metropolitan University, we use 10X field and look at a minimum of 200 sperms.

Hope that helps.

Stephane