This is Stephanie from StatisticsHowTo.com.

And in this video I will go over a few problems that involve the probability of something

not happening. I am going to go over three different question

types. The first type of question you are likely

to encounter is one like this. If the probability a major hurricane will

hit Florida this year is 0.49, then what’s the probability a major hurricane does

not hit Florida this year? We take 100 percent and you subtract the given

probability. This is given as a decimal it is 0.49.

I am going to change that to a percentage, 49 percent that gives me 51 percent.

If you don’t want to deal with percentages instead of a 100 percent.

We could just say 1 and then we can subtract the decimal 0.49 and that will give you 0.51.

That brings me to my second problem type. This time we are given 27 percent of Americans

support Universal Health Care. If an American adult is chosen at random.

What is the probability they will not support Universal Health Care?

Well we have got 27 percent this time, so we can subtract that directly from 100

percent that gives us 73 percent. 73 percent of adults will not support

Universal Health Care. Unfortunately, figuring out the probability

of an event not happening is not always that easy.

Got a slightly more complicated question here. We have got 12,942 construction workers injured

by falling debris. A list of cities.

And a question is asking if an injured construction worker is selected at random.

What’s the probability the selected worker will have been injured in a city other than

Houston, Miami, or Denver? In other words what is the probability the

event did not take place in one of these three cities?

Let us start by adding up the numbers. We are given a total of 12,942 constructions

workers and we are given numbers of injuries. For Houston we are given 219, for Miami we

are given 112 and for Denver we are given 140.

So let us add those up. And that gives us 471 injuries that happened

in those places. In other words, 471 out of 12,942 injuries.

This is a fraction. If I divide through, I got a decimal and that

is .0364. This is the probability that an injury will

take place in one of those three cities. But we want the probability of it not happening.

So subtract from 1. That gives us 0.9636 and I am rounding to

four decimal places here. That is how to find the probability of an

event not happening. Check us out at StatisticsHowTo.com for more

videos and articles on everything elementary statistics.

Superior Construction Pte Ltd is a successful company dealing with many major projects in Singapore. Recently, it has submitted its biddings for two major Government projects. Project A worth about $120 million and the company believes it has 40% chance of securing the project. Project B worth $1.8 billion and there is 30% chance the company can win the project. Both project are independent of each other. What is the probability that the company

will not secure Project A or will not secure Project B ??

on the last problem, why can't you just take the probability of NY and SF 251/12,942 since those are cities not in the ones mentioned by the question? Thanks!

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