Question

A type of lightbulb is labeled as having an average lifetime of 1000 hours. it's reasonable to model the probability of failure of these bulbs by an exponential density function with mean=1000. use this model to find the probability that a bulb i) fails within the first 200 hours ii) burns for more than 800 hrs

Answer 1

The set up should look like this:
Pr(x≤200)=∫0200(1/1000)e^−1/1000x dx