SIR Step 3

Calculate the expected number of cases given the incidence rate in your reference population. How does one calculate the expected number of cases?

1. the person-time accumulated in our study group
2. the total number of cases observed, and
3. the incidence rate of neurological disorders in the general population.

[Hint: Keep in mind the definition of an incidence rate (# Cases/Person-time of Observation)].
Expected Cases = (Person-time accumulated in our study group) * (The incidence rate of neurological disorders in the general population)

SUPERCLEAN Employees			Epiville
Age (Yrs) (1)	N (Person-Time) (2)	Observed Cases (3)	Incidence Rate Per PYO' s (4)	Expected Cases (2*4)
20-25	5114	47	0.00039	- 1 2 3 4
25-30	6048	71	0.00052	- 1 2 3 4
30-35	5442	61	0.00047	- 1 2 3 4
35-40	1071	15	0.00062	- 1 2 3 4
Total		194	0.002	- 7 8 9 10

[ Definition ] [ Step 1 ] [ Step 2 ] [ Step 3 ] [ Step 4 ] [ Step 5 ]