Significance of third decimal place

[Guest guest]

Vidyasankarji :

 

I agree that the third decimal place would be significant

in Bamshad, et. al., "Genetic Evidence on the Origins of

Indian Caste Populations", IF they had them.

 

But I do not see how they can have results to that significance.

E.g., in table two, the standard errors for estimation of

frequency of the M Haplogroup are 5.5, 3.8, 5.3% respectively

for Upper, Middle and Lower caste groups. Yet distances in

table 1 are given to 3 decimal places.

 

How can it be any different for Y-chromosome stuff, unless

Y-chromosomes are much more uniform than mtDNA (not).

Yet table 3 is given to four significant figures.

 

 

Table 3. Y Chromosome (STRs) Genetic Distances

between Caste Groups from Andhra Pradesh and

Continental Populations

 

Caste group Africans Asians Europeans

Upper .0166 .0104 .0092

Middle .0156 .0110 .0108

Lower .0131 .0088 .0108

All castes .0151 .0101 .0102

 

An explanation would be most welcome.

-Arun Gupta

[Guest guest]

I am trying to dig out the research behind the statistics, and

the models of genetic drift that are presumed in comparative

analyses. The numbers reported are usually based on 90% or 95%

confidence level estimations. I'll share more information when

I find out more.

 

As of now, what I do know is that different markers are known to

have different statistical distributions, so the autosome data

(Table 5 in Bamshad et al.) and the biallele data (Table 4) in

Y-chromosomes would be different, with the latter changing at a

faster rate than the former. The HVR (hyper-variable region) in

a gene (one of the other tables ... don't have the paper at hand

now), as its name implies, is subject to lots of mutation, and

is more diverse, as compared to conserved regions. So the number

of significant digits in any reported number would vary with the

specific genetic marker being investigated. Meanwhile, see today's

Times of India, for a related feature by Chidanand Rajghatta of

Washington DC.

 

Vidyasankar