Cohort Study: SIR Step 3
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?
- the person-time accumulated in our study group
- the total number of cases observed, and
- 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)
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| 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 | |
| 25-30 | 6048 | 71 | 0.00052 | |
| 30-35 | 5442 | 61 | 0.00047 | |
| 35-40 | 1071 | 15 | 0.00062 | |
| Total | 194 | 0.002 | ||
[ Definition ] [ Step 1 ] [ Step 2 ] [ Step 3 ] [ Step 4 ] [ Step 5 ]
