are listed in the order of their expected development.
Each item lists criteria for determining when the child
has sufficiently mastered a skill and can move to more
advanced skill. Finally, in each curriculum sequence
items are grouped in age span, i.e. an interval time ex-
pressed in months that is a multiple of 3. So, each se-
quence is divided in to multiple items (so called in the
CC) that are age-dependent, i.e. each item describes
a skill that a child should acquire in a predetermined
month interval. Each item is a precise ability that the
child has to prove he knows how to do it.
2.2 Definitions
The CC does not assume that a child will develop at
the same rate across domains and the skills belong-
ing to a domain are unrelated to skills belonging to
other domains. We can study a generic domain, cal-
culate the age level in that domain, and then apply the
formulas to all the domains of the CC.
We will define the observation of a skill expressed
by each item as s
i
and each item can have value 0,
0.5 or 1 accordingly that the observers deduce that the
child does not have that skill, he quite has it, or he def-
initely has the skill. This is made in accordance with
the convention of the Assessment Log, which states
to tag each item with a plus (+) for skill the child has
mastered, a plus/minus (+/−) for an inconsistent or
emerging skill, and a minus (−) for a skill that the
child is unable to do. Observe that a child might have
or not the skill in a specific time, so, each s
i
must be a
function of time t, where the observer, in a particular
time, evaluates the skill, so that it will be s
i
(t) ∈ [0,1].
We also define a chronological age function, c(t),
of the child that is expressed in months (i.e. if the
child had 2 years 4 months and 15 day, then we write
24.5 months). The function c(t) is a function of time,
that has meaning from the date of birth, db, and will
be defined as
c(t) = t −db.
As for time t we also define an entering date t
0
in
which we establish the first time, among all the skills,
what the child has acquired or not. Then, there will be
an appropriate number of evaluation dates t
n
, where n
will vary across the total number of interventions that
will be necessary. Moreover at each evaluation date,
there will be an Item Rating in which the skills are
evaluated: s
i
(t
n
).
It is important to notice that the skills are age-
dependent, and some skill might be linked to ages
that are above the chronological age of the child. If
they were reported they would indicate some sort of
advanced performance of the child, and so an high de-
velopment rate (DR). To overcome these problems it
is important to define more precisely the s
i
, and their
use in the CC.
Parents, aid and professional, can be considered
as the observers of a phenomenon, which is the evo-
lution of a child that is acquiring new skills over time.
These observes can not assist this evolution second by
second, but at a certain time t
n
they observe the child
and deduce the level at which the child masters such
skill. So the only observables are: the skills s
i
and
the child chronological age c(t). The second is eas-
ily known, but the evaluation of the skills is not so
simple. In general, each skill can be considered as a
number that can vary from 0 to 1, and is a function
of the chronological age, and so a function of time.
Each function s
i
(c(t)) will indicate at a certain time
c(t) of the chronological age of the child how much
he is able to express that skill, moreover since the lin-
earity of c we will not always indicate such function
for the sake of briefness. So we will define a function
s
i
(t): [0,+∞) → [0,1].
Next, it is useful to associate at each observable
function s
i
(t), a standard function ¯s
i
(t), which will
indicate the typical period to obtain such skill. At
this standard functions (as well as to the observable
one) we will associate a month n
i
indicating when the
skill usually arises, and a month m
i
that indicates the
month, after which the skill is fully developed, and a
function f
i
(t) that indicates how the skill is obtained
in the period [n
i
,m
i
]. This function will be defined
¯s
i
(t) =
1, c(t) ≥ m
i
f
i
(c(t)), n
i
≤ c(t) ≤ m
i
0, c(t) ≤ n
i
.
These hypothesis are consistent with the concept of
age span in the CC.
Unfortunately the functions f
i
in ¯s
i
(t) are un-
known, and the CC books does not give enough de-
scriptions on how to correctly define such functions;
this is reasonable, since the CC is a curriculum-based
assessment.
It would be preferable to not fix any sort of hy-
pothesis on f
i
, but we will see that in order to evaluate
the skill of the child when his age does not coincide
with any of the n
i
or m
i
, we will have to specify f
i
,
and the simplest hypothesis that we can given is that
they are linear, i.e.
f
i
(t) =
c(t) − n
i
m
i
− n
i
.
The goal will now be to estimate the age of a child
with respect to a particular domain, i.e. DA(t) that
will express the development age of the child within a
AMathematicalFormulationforEstimatingAgeLevelsintheCarolinaCurriculum
263