I also assumed that the uncertainties represent two standard deviations.
This is not the conventional assumption.
When I wrote c = 1.08 ± .01 the error bar (.01) was intended
to represent _one_ standard deviation. This is longstanding
standard practice.
Reference: Taylor, page 14.
In more detail:
Unless otherwise specified very explicitly:
-- For a Gaussian, each error bar is one standard deviation.
Note that this is approximately equal to the HWHM.
The + and - error bars together cover 68% of the probability.
-- For a triangular distribution, each error bar is exactly
one HWHM. The + and - error bars together cover 75% of the
probability.
-- For a square distribution, each error bar is exactly one
HWHM. The + and - error bars together cover 100% of the
probability.