Life Tests with Periodic Change in Failure Fate

In this paper two life testing procedures viz., the progressively censored samples and Bartholomew's experiment have been discussed under the assumption that the failure rate of an item is constant, though different under the two different conditions of usage at regular intervals. The estimates of the two failure rats have been derived alongwith their asymptotic variances for both types of data, i.e., when the failure times are recorded and when only the numbers of items failing in each interval are recorded. Numerical examples have been worked out to illustrate the type of data and relevant calculations.