An exponential distibution is used to model the time between events occuring or the wait time for an event. It assumes that events are independent of each other. It also has a key property of being memoryless. Some applications include time until an electronic component breaks, or waiting time until the next phone call at a customer service center.
Where ${\lambda}$ is the rate, related to ${1 \over mean}$.
If cummulative is set to True, the the cummulative distribution function is returned. The formula for this is:
${1 - e^{-x \lambda}}$
If cummuulative is set to False, the probability density function is returned. The formula for this is : ${\lambda e^{-x \lambda}}$
In the Power BI formula bar define the following measures:
prob density = EXPON.DIST(1,2,false)
This returns the following formula:
cummulative distribution = EXPON.DIST(1,2,True)
The lifetime of a lightbulb follows a exponential distribution with a mean value of 0.5 years. Find the probability that the light bulb dies in the first year: