# Basic Probability

## Exploring the World of Probabilities in Everyday Scenarios

In our daily interactions, we often use words like "likely", "probably", and "certain" to express the chances of something happening. For example, we might say "it's likely to rain later" or "I'll probably not finish my work". These words are all part of the language of probability, which also includes phrases like "impossible" and "even chance". If you pay attention to the news, you'll spot these probability buzzwords being used frequently.

In this article, we'll delve into the basics of probability theory, including its core formula and real-world applications.

## Recapping the Foundation of Probability Theory

Using mathematical principles, we can assign a numerical value to the likelihood of an event occurring, instead of relying on just descriptive words.

First, let's define what we mean by an "event". An event is any possible outcome that results from a random experiment, typically represented by a capital letter (e.g. A, B, C). In terms of probability, an event is considered as a subset of a sample space - a set containing all the potential outcomes of an experiment, usually denoted by the Greek letter Ω (omega) or the letter S.

If an event is certain to occur, its probability is 1. For instance, the probability of tomorrow being Tuesday, given that today is Monday, is always 100%.

On the other hand, if an event is impossible, its probability is 0. For example, the probability of tomorrow being Tuesday, given that today is Thursday, is 0 because it can never happen.

For instance, if you toss a coin, there's an equal chance of getting "heads" or "tails", meaning there's a probability of 0.5 for each outcome.

Note that probabilities always fall between 0 and 1, representing impossible and certain events, respectively. Probability cannot be negative or greater than 1. In most cases, events will have a chance of occurring between these extremes, and probabilities can be expressed as fractions, decimals, or percentages.

Remember, a probability can never exceed 100% or go below 0%.

## Understanding the Basics of Calculating Probabilities

There are two main types of probabilities: theoretical and experimental. Theoretical probabilities are determined through reasoning and knowledge of a particular situation, while experimental probabilities are based on the results of an experiment and used to predict future events.

There is also a third type of probability known as axiomatic probability, but it's beyond the scope of this article.

For our purposes, we'll focus on theoretical probability and use it to examine the properties of a six-sided die. We'll also introduce the fundamental probability formula.

## The Basic Probability Formula

Let's say we roll an unbiased, six-sided die - what's the probability of rolling a 3?

First, we need to identify the sample space, which in this case is the set of all possible outcomes: 1, 2, 3, 4, 5, 6. Since the die is unbiased, we know that each outcome is equally likely. Therefore, the probability of rolling a 3 is 1/6.

In fact, for any outcome, the probability can be calculated using the following formula:

P(A) = number of outcomes in A / total number of possible outcomes

In our die example, there is only one way to roll a 3 out of a total of 6 possible outcomes. Hence, the probability of rolling a 3 is:

P(3) = 1/6

We can also use this formula to determine the probability of an event not occurring:

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

Using set notation, this can be written as:

P(A') = 1 - P(A) = 1 - (number of outcomes in A / total number of possible outcomes)

For example, what's the probability of not rolling a 4 or 5?

This is equivalent to asking for the probability of any other outcome (1, 2, 3, or 6), which can be calculated by subtracting the probability of rolling a 4 or 5 from 1:

P(not 4 or 5) = 1 - P(4 or 5) = 1 - (2/6) = 4/6 = 2/3

## Examples of Calculating Basic Probabilities

To fully grasp the concept of calculating probabilities, it's essential to practice with more examples.

## Basic Probability: Exploring the Likelihood of Simple Events

Probability is a crucial concept in comprehending the likelihood of simple events like flipping a coin or rolling a die. In this article, we will delve into the fundamentals of probability and its different types.

### Formula for Basic Probability

The formula for basic probability is easy: it is the number of desired outcomes divided by the total number of outcomes. For example, if we toss a fair die once, the total number of outcomes is 6 and the number of desired outcomes (getting an even number) is 3. Therefore, the probability of getting an even number is 3/6, or 0.5.

### Types of Probability

There are three types of probability: theoretical, experimental, and axiomatic.

• Theoretical probability is based on reasoning and theoretical knowledge of a specific situation. It is often used to determine the probability of simple events.
• Experimental probability, on the other hand, uses the outcomes of an experiment to infer the probability of an event occurring in the future. For example, if we flip a coin 100 times and get 50 heads and 50 tails, we can infer that the probability of getting heads is 0.5.
• Axiomatic probability, also known as classical or mathematical probability, is based on mathematical principles and assumes that all possible outcomes are equally likely.

### Examples of Basic Probability

Some common examples of basic probability include flipping a coin or rolling a die. For instance, the probability of getting 'heads' when flipping a coin is 0.5 since there are only two possible outcomes (heads or tails) and they are equally likely.

### Solving Basic Probability Problems

To solve basic probability problems, we can use mathematical equations and logical reasoning. It is important to note that probabilities always range from 0 to 1. A probability of 0 means that the event is impossible, and a probability of 1 means that the event is certain to occur. Most probabilities fall somewhere in between, with some being more likely to occur than others.

In conclusion, having a grasp of basic probability is crucial in analyzing and predicting the likelihood of simple events. By utilizing the basic probability formula and employing reasoning and logic, we can solve a wide range of probability problems.