I need to analysis the failure of some physical machines in public data set to estimate the reliability. There are enough samples to find which distribution function these physical machines follow. However, the samples and information captured only very small period of lifespan of these physical machines and these period of time does not show in which stage of life (early, useful, and wearout) was captured.
Can I assume these physical machines follow exponential distribution, because the lake of information. And use non-parametric methodologies to estimate the parameter.