What is the probability? Find out now!

Have you recently started out with your Statistics class and are wondering as to what is the probability? See, there are a number of events that cannot be predicted with utmost certainty. For this purpose, these events and their outcomes are expressed as being ‘likely’ to occur with the help of probability. For instance, the best examples of probability include: whenever we toss a coin, there aren’t any sureties with regards to its outcome. The possible outcomes are two: either it would result in heads (H) or tails (T). In such a condition, probability statistics claims that the probability of the coin landing on heads or H is ½, whereas the probability of the coin landing over tails is also ½. This can be shown over a probability table and probability Venn diagram as well. Here is a probability tree diagram for the same:
probability tree diagram

Generally speaking, the basic probability notation or formula is:

Probability of an event happening 


Number of ways it can happen


Total number of outcomes


Probability rules that you should know about

There are certain probability rules with basic probability terms that you should know about for the effective outcome of your problems. Here’s a look into them:

1. The rule of subtraction

The math probability rule of subtraction states that the probability that an event named A is going to take place is equal to 1 subtracted out of the probability that it will not take place. In general:

P(A) = 1 - P(A')

2. The rule of multiplication

Out of the many different rules of probability, the probability multiplication rule is applicable only in instances where you wish to acquire the probability of the intersection of two varying events. The rule states that the probability that both events A and B are going to occur equals the probability that event A takes places multiplied by the probability that event B will take place in cases wherein event A has already taken place. Hence:

P(A  B) = P(A) P(B|A)

3. The rule of addition
This particular rule is applicable in situations wherein there are two events and we wish to acquire the probability that either of them would take place. The general rule to be followed here is this:

P(A  B) = P(A) + P(B) - P(A  B))

Information about types of probability

When you start learning about what is probability in math, you would find out that the probability theory states that there are three types of probability. These are known as:

1. Classical frequency
2. Relative frequency
3. Subjective frequency

A few probability examples

Here are a few probability examples to help you acquire probability homework help. This probability help is going to prove very beneficial for you. These are basically probability questions that you need to answer:

There are 4 equal sectors in a spinner that are colored yellow, green, red and blue. When the spinner is spun, what is the probability that it will land on green?

Now, there are 4 outcomes of this experiment, which shows that:



# of ways to land on green



total # of colors


Intro to Probability Video Lesson

More topics in Probability
Empirical Probability Theoretical Probability
Experimental Probability Binomial Probability
Calculating Probability Probability Problems
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