  We perform a multiparameter likelihood analysis to compare measurements of
the cosmic microwave background (CMB) power spectra with predictions from
models involving cosmic strings. Adding strings to the standard case of a
primordial spectrum with power-law tilt n, we find a 2-sigma detection of
strings: f_10 = 0.11 +/- 0.05, where f_10 is the fractional contribution made
by strings in the temperature power spectrum (at multipole l = 10). CMB data
give moderate preference to the model n = 1 with cosmic strings over the
standard zero-strings model with variable tilt. When additional non-CMB data
are incorporated, the two models become on a par. With variable n and these
extra data, we find that f_10 < 0.11, which corresponds to G mu < 0.7x10^-6
(where mu is the string tension and G is the gravitational constant).
