Dictionary of Evidence-based Medicine.pdf

Dictionary of Evidence-based Medicine 83
Figure 11 Identification of cases included in the calculation of incidence and prevalence
Incidence study (see also under Cohort study)
A study in which subjects are recruited and followed forward in time so
that the rate at which particular events of interest occur can be recorded to
enable calculation of incidence.
Incremental cost
The incremental cost is the difference between the cost of an intervention
and the cost of the programme to which it is compared. More generally, the
term 'incremental cost' is used synonymously with the term 'marginal
cost' which is the cost of producing the last unit of product, as illustrated
in Table 2 below.
Table 2 The relationship between average and marginal costs
Output Average cost Total cost Marginal cost
1
2
3
4
5
6
7
10
8
7
6.25
5.8
5.8
6
10
16
21
25
29
34.8
42
Note that the marginal cost is calculated by subtracting from the last total cost, the previous total.
10
6
5
4
4
5.8
7.2