Stock sampling

[clarification needed] This is in contrast to flow sampling, where the relationship of interest deals with duration or survival analysis.

[2] Imposing the same model on data that have been generated under the two different sampling regimes can lead to research reaching fundamentally different conclusions if the joint distribution across the flow and stock samples differ sufficiently.

This selection issue is akin to the truncated regression model where we face selection on the basis of a binary response variable, but the problem has been referred to as length-biased sampling in this specific context.

), there is a high likelihood the short duration spells will be omitted from the sample, as some durations shorter than 12 months are necessarily omitted from the sample:[2] A number of methods to adjust for these sampling issues have been proposed.

One can appropriately adjust the maximum likelihood estimation for censored flow data for the sample selection, or use nonparametric estimation methods for censored flow data for the sample selection, or use nonparametric estimation methods for censored data.