By Science News
Significant issue
It is quite sad that your otherwise-excellent publication systematically fails to report error bars in your reports. Time and again I read articles and am left wondering whether the effect reported is even statistically significant. As just one example, “Treatment helps newborns avoid HIV” (SN: 10/25/03, p. 270: Treatment helps newborns avoid HIV) said that the rate of subsequent infection from breast milk dropped from 12 percent to 8 percent. Given the numbers in each sample, it is quite likely that the difference reported is simply due to chance.
Kevin Lehmann
Princeton University
Princeton, N.J.
The results cited in the story were significant at a probability greater than 95 percent. As a general rule, for the sake of readability, Science News doesn’t include statistics on the significance of data. Readers should rest assured, however, that we don’t report results if a statistical test has failed to find them significant.–The Editors
No dark secret
In 1993, Israeli physicist Moti Milgrom showed an adjustment to the way gravity is calculated that would make dark matter go away in Newton’s system for calculating gravity. If Milgrom’s math were used in the survey for dark matter in “Cosmic Survey: Galaxy map reveals dark business as usual” (SN: 11/1/03, p. 275: Cosmic Survey: Galaxy map reveals dark business as usual), would it also make dark matter go away?
O. Frank Turner
Westminster Colo.
Most astrophysicists would say they still see the need for dark matter in the universe.–R. Cowen
Six-foot-deep symbolism
A simpler explanation for ancient humans’ use of red ocher might be cosmetics, much as in modern mortuary practice (“Stone Age Code Red: Scarlet symbols emerge in Israeli cave,” SN: 11/1/03, p. 277: Stone Age Code Red: Scarlet symbols emerge in Israeli cave). A dusting of red ocher would offset the blue pallor that results when blood flow ceases. No deep, dark symbolism was necessarily involved.
Virgil H. Soule
Frederick, Md.
Any mortuary practice involves symbolism. Simply burying a person’s body instead of leaving it where it lies invokes symbolic thinking.–B. Bower
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