least 10% of typical children of any age, in other
words, unusual errors) using data from Dodd et al.
(2002).
Local dialect was taken into account when judging
whether an error had occurred. For example, in
the central belt of Scotland a glottal stop replaces
word medial and final /t/ most of the time (Scobbie,
Gordeeva, & Matthews, 2007), so when this
occurred, it was not counted as an error. Although
all of the children’s errors were described in terms of
processes, this does not necessarily suggest that the
errors were the result of a phonological impairment.
While it is possible that some errors might be
phonological in nature, for example fronting of /k/
to [t], other processes were more likely to be
phonetic in nature, for example, lateralization and
other distortions. For the purposes of the analysis all
errors were counted together. In addition to calculating
the number of times an error type occurred,
the number of children displaying an error type
three or more times (Dodd et al., 2002) was
also calculated. Although each phoneme was only
sampled three times in the data, most processes
apply to classes of sounds rather than individual
phonemes. In the case of phoneme specific nasal
emission, this usually affected /s/ which was sampled
more than three times due to the inclusion of
s-clusters in the test. This enabled us to identify
whether errors occurred only occasionally in a child’s
speech or whether they were more prevalent. It also
allowed us to determine how many children in the
group presented with each error type.