The exponential distribution is typically used to model waiting times, for example, to model survival times of cancer patients or life times of machine components. Often these are waiting times between the events of a Poisson distribution. The exponential distribution is memoryless in the sense that the remaining waiting time at a specific time point is independent of the time which has already elapsed since the last event. The parameter can be seen as a constant failure rate (failures over a specific unit such as hours).
Description:  Tests if the parameter of an exponential distribution differs from a specific value . 
Assumptions: 

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