0
$\begingroup$

Suppose

$D_i=$ Observed number of deaths in the age group $(x_i, x_{i+1})$,

$P_i=$ Mid-year population for age group $(x_i, x_{i+1})$,

$N_i=$ Number of people alive at $x_i$ among whom $d_i$ deaths occur.

I can't distinguish between $P_i$ and $N_i$. What is the difference between $P_i$ and $N_i$?

$\endgroup$

1 Answer 1

1
$\begingroup$

The number of people alive $(N_i)$ is the number at the start of the time period so the number at risk of dying during the following year. The mid-year population $(P_i)$ is just that, the number alive at the middle of the time period under study. This can be used, for instance, if you want to estimate the number of person-years that population were at risk of something like an illness or accident. You cannot use $N_i$ to calculate person-years at risk because, especially at advanced ages, many will die part way through the year.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.