I´m calculating the genetic variance of some variables such as yield and fruit weight from the mean squares of the analysis of variance, and the genetic variance gives me negative, Why, this variance gives negative and how is it done to calculate the coefficient of genetic variation with negative variances?
can anybody help me? please
No sqr!!! Your response should be (Editable(T|F), weight, color, ..) product.
Hi,
Variance always should be positive, I thing there is some thing wrong, could you show us the data and recheck it again
Hi Liz,
I agree with Hazhar because it is a sum of squares. Show us only one variable.
Regards
Variance can never be negative. Since genetic variance has been obtained negative, it is certain that some error has been committed either in selecting / applying the formula(s) correctly or in the computational steps.
Thorough verification is required in detecting the error(s) committed.
"mean squares of the analysis of variance" is already a variance. We can further discuss if you could provide which formula you are using for calculating genetic variance.
Thanks everyone for your help. The formula I´m using to calculate the genetic variance is Vg= (mean square of genotypes - mean square of genotypes x environment) / (number of environments x number of replications).
Thanks
Numerator of this formula is actually difference of two variances which can be negative. I think, we need to interpret the negative value of this formula. In this regards, some peer in the field of genetics can help. It is not the issue of negative variance.
Negative genetic variance could be due to sampling error and lack of non-random mating and are replaced by Zero during computing. The true values are small positive quantities (Comstock and Robinson, 1948).
@ John Charles Aru, I don't agree that the genetic variance could be negative due to sampling error and lack of non-random mating and are replaced by Zero during computing.
I already mentioned that variance can never be negative. Since genetic variance has been obtained negative, it is certain that some error has been committed either in selecting / applying the formula(s) correctly or in the computational steps. Therefore, thorough verification is required in detecting the error(s) committed whether in applying the formula or in computations.
@ Hafiz Arshad,
Numerator of this formula is the difference between two variances, however, it is the subtraction of a smaller variance from a larger variance. Hence, it can't be negative. I am sure that some error has been committed either in selecting / applying the formula(s) correctly or in the computational steps.
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