Statistical Errors: Chakraborti's Response

Marimuthu reported two errors in our paper (1). First, I would like to respond to his comment that we had omitted 1.1% of the values (121 cases). In our original manuscript, we provided actual values up to one decimal place, but because of overlapping of the numbers in our Figure 2, we rounded off the values. The actual values are 27.7, 14.2, 10.2, which equals the missing 1.1% that Marimuthu reported as our first error. However, one can easily see in the Y-axis of our Figure 2 that the bar for [is less than] 10 [micro]g/L arsenic in Bangladesh is nearer 28% than 27% (the actual value is 27.7%) even though the number above the bar is 27.

The second error reported by Marimuthu came about when we converted values from milligrams per kilogram to micrograms per kilogram. The actual value is 15,500 (not 1,550). However, it is easy to see that there is an error in a number because the maximum value can not be 1,550 when the mean and median values are 6,820 and 4,460, respectively. Correlation coefficients between hair, nail, urine, and water arsenic were discussed by Biswas et al. (2), which we referenced in our paper.

Finally, we appreciate Marimuthu's mode approach for statistical evaluation of data, and we will keep his suggestion in mind.

REFERENCES AND NOTES

(1.) Chowdhury UK, Biswas BK, Chowdhury TR, Samanta G, Mandal BK, Basu GC, Chanda CR, Lodh D, Saha KC, Mukherjee SK, et al. Groundwater arsenic contamination in Bangladesh and West Bengal, India. Environ Health Perspect 108:393-397 (2000).

(2.) Biswas BK, Dhar RK, Samanta G, Mandal BK, Chakraborti D, Faruk I, Islam KS, Chowdhury MM, Islam A, et al. Detailed study report of Samta, one of the arsenic-affected villages of Jessore District, Bangladesh. Curr Sci 74(2):134-145 (1998).

Dipankar Chakraborti School of Environmental Studies Jadavpur University Calcutta, India E-mail: dcsoesju@vsnl.com

COPYRIGHT 2001 National Institute of Environmental Health Sciences
COPYRIGHT 2004 Gale Group