For interval data, the maximum likelihood estimates, , satisfy the following equations:
The standard errors are the standard deviations of the estimate of the parameter. The standard errors are calculated as the square root of the appropriate diagonal element of the inverse of the Fisher information matrix.
|Yi||retirement time for the ith system|
|tij||interval endpoints for the ith system|
|ki|| number of failures for the ith system|
|Nij||number of failures in an interval|
|N||total number of systems (in each growth curve)|