How to calculate the probability?

Irina Fateeva
Irina Fateeva
February 19, 2013
40286
How to calculate the probability?

So, let's talk on a topic that interests a lot of people. In this article I will answer you the question of how to calculate the probability of an event. I will give formulas for such a calculation and a few examples to make it clearer how this is done.

What is the probability

To begin with, the probability that an event will occur is a certain amount of confidence in the final onset of a result. For this calculation, a formula for the total probability has been developed, which allows to determine whether an event of interest to you will occur or not, through so-called conditional probabilities. This formula looks like this: P = n / m, the letters can change, but this does not affect the essence itself.

Probability examples

In the simplest example, we analyze this formula and apply it. Suppose you have some kind of event (P), let it be a roll of a die, that is, an equilateral dice. And we need to calculate what is the probability of 2 points on it.To do this, you need the number of positive events (n), in our case - the loss of 2 points, the total number of events (m). The loss of 2 points can be only in one case, if the cube has 2 points each, since differently, the amount will be larger, it follows that n = 1. Next, we count the number of loss of any other numbers on the bone, on 1 bone - these are 1, 2, 3, 4, 5 and 6, therefore, favorable cases of 6, that is, m = 6. Now, using the formula, we make a simple calculation of P = 1/6 and we see that 2 points are 2 points on the dice, that is, the probability of an event is very small.

We also consider an example on the colored balls that are in the box: 50 white, 40 black and 30 green. You need to determine what is the probability of pulling the ball of green. And so, since the balls of this color are 30, that is, there can be only 30 positive events (n = 30), the number of all events is 120, m = 120 (by the total number of all balls), using the formula, we expect to pull out the green ball the probability equal to P = 30/120 = 0.25, that is, 25% out of 100. In the same way, you can calculate the probability of pulling a ball of a different color (black, it will be 33%, white is 42%).

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