X-rays from Source 3C 273

Friedman and Byram (1) describe a high-altitude x-ray experiment and give the results obtained from a single scan through the Virgo region. In addition to M 87, the authors claim to have detected four other x-ray sources, one of them in the direction of the quasar 3C 273. Unfortunately they do not give standard deviations for their calculated flux values, and it is therefore necessary for the critical reader to make his own estimate of the statistical significance of the results. This can be done in a variety of ways, three of which will be described briefly. In each case we deal only with that part of the record between the beginning of the controlled