A study of residential 60-Hz magnetic field levels was conducted in
the Midwest. 51 homes in the Twin Cities (Minnesota, N=24) and
Detroit (Michigan, N=27) were selected to participate based on a
random digit dial sampling scheme. Each home was visited 7 times,
approximately every two months. At each visit, an Emdex-C electric
and magnetic field (EMF) data-logging meter (Emdex-C) was used to
collect EMF levels over a 24 hour period. 24-hour measurements are
taken from spot measurements every 30 seconds. An Emdex-C was
placed in a child's bedroom under the bed and in the kitchen of each
home. Households were offered $10 per completed visit for the first
six with $40 payable upon completion of the seventh visit.

The response of interest is the (base 10) log-transformed 24-hour-mean
EMF measurement. The response is additionally multiplied by 100 in
order to facilitate the estimation of variance components. There are
19 missing log EMF values. The wiring configuration of each house was
also recorded and is coded on the four point Wertheimer-Leeper scale
here.

These data courtesy of Dr. William Thomas at the University of Minnesota.