An obviously useful check is to examine whether the data are consistent
with the beliefs expressed about them. The simplest way of doing this is
to standardise the data. Our notation for the standardised value of a
datum 
is 
. For the data we saw, 
and
,
The observation 
might be a little suspect: the Doctor's two-hour
reading is more than two standard deviations distant from her
expectation. The fasting measurement 
is just over one
standard deviation from her expectation.