© 1998 by Biometrika Trust
MISCELLANEA |
Testing whether a survival distribution is new better than used of an unknown specified age
Division of Statistics, Northern Illinois University DeKalb, Illinois 60115, U.S.A. ahmad{at}math.niu.edu
A survival variable is a nonnegative random variable X with distribution function F and a survival function
This variable is said to be new better than used of specified age t0 if
for all x
0 and a fixed t0. Testing
for all x
0 against
when the point to is unknown but can be estimated from the data is proposed when t0 = µ, the mean of F, and also when t0 =
p, the pth percentile of F. It is shown that, while the known tests for known t0 (Hollander, Park & Proschan, 1986; Ebrahmi & Habibullah, 1990) continue to hold when t0 = µ and is estimated by
, a simpler and distributionfree test is possible when t0 =
p and is estimated by X([n,p]). The performance of this test is presented.
Key Words: Asymptotic normality Estimated parameters Percentiles Pitman asymptotic efficiency U-statistics