Hello Everyone,
I need a little help I analyzed sequences by tajima's D and fu's Fs neutrality tests and I found negative values for Tajima's D and a not significant p value as well as for fu's fs I found some positive values and the p value is not significant, what does that mean?
Hello Othmane Daoui
What software did you do this with? Would you like to explain a little?
Othmane Daoui , Tojima's D can be become negative if there is an excess of rare alleles in the population after fixation of an advantageous allele, i.e. the effect of an advantageous mutation going to fixation in the population. The reason for this is that, in the formula of Tojima's D statistics above, the estimator $\theta_2$ (θ2) will be higher than $\theta_1$ (θ1) , where θ1 is an estimator that assigns more weight to alleles segregating at intermediate frequencies while θ2 weights all categories equal. However you should be careful in interpreting the sign of the point estimator, as the p-values suggest that the difference is not statistically different from zero (i.e. is not positive nor negative). Have in mind also that uncertainty regarding genotypes and the effect of sequencing and mapping errors could be causing a bias. I am a Bayesian, so I would suggest to use instead a Bayesian approach as described here for example:
Article Calculation of Tajima’s D and other neutrality test statisti...
- Badges
- Science topic
- Similar topics
- Mathematical Sciences
- Graphs