# Geometric distribution probability of no success at all

From S. Broverman, 2006:

A town's maintenance department has estimated that the cost of snow removal after a major snowstorm is $$100,000$$. Historical information suggests that the number of major snowstorms in a winter season follows a geometric distribution for which the probability of no major snowstorms in a season is .4. The town purchases an insurance policy which pays nothing if there is one or less major snowstorms in the season, but the insurance pays $$50$$% of all seasonal snow removal costs for major snowstorms if there are $$2$$ or more major snowstorms. Find the expected payout by the insurer.

I am confused by the bolded line "a geometric distribution for which the probability of no major snowstorms in a season is $$.4$$". That sounds like it is saying the probability of no success at all is $$.4$$.

How does one find the probability of no success in a geometric distribution? From here it seems that one simply takes $$(1-p)$$ to the power of the $$n$$th attempt for which there is no success. However, according to that, how does one find the probability of no success at all, no matter how many attempts? Wouldn't that be $$\lim \limits_{n \to \infty}(1-p)^n = 0$$? If so, how would one understand the probability of no success being $$.4$$?

• As explained [here] the term "geometric distribution" is ambiguous, but I take it to mean that the probability of exactly $k$ snowstorms is $p(1-p)^k$ with $p=.4$ – saulspatz Jan 14 at 17:00
• Thank you, was there supposed to be link in the "[here]"? – agblt Jan 14 at 17:05
• Yes there was: en.wikipedia.org/wiki/Geometric_distribution Sorry – saulspatz Jan 14 at 17:33

From saulspatz's comment, I gather that the way to interpret the geometric distribution here is that success is "the point at which the snowstorms stop", and $$p$$ is the probability of the snowstorms stopping. Failure is that there was a snowstorm, therefore making it that the snowstorms did not yet stop.

Hence one can use the definition $$p(1-p)^k$$, and at $$k=0$$, this would mean that there was no failure because the snowstorms never started.

One can also use the definition $$p(1-p)^{k-1}$$ and at $$k=1$$, this would mean that on the first attempt, the snowstorm stopped, never starting.