Probability & statistics for engineers & scientists

  • anticipation
  • chance
  • contingency
  • expectation
  • feasibility
  • odds
  • possibility
  • prospect
  • chances
  • conceivability
  • credibility
  • hazard
  • liability
  • likeliness
  • plausibility
  • practicability
  • prayer
  • presumption
  • promise
  • reasonableness
  • shot
  • toss-up
  • outside chance
  • snowball's chance

Roget's 21st Century Thesaurus, Third Edition Copyright © 2013 by the Philip Lief Group.

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How to use probability in a sentence

The probability an interval had zero signals was the probability that the first source didn’t emit a signal, 1−p, times the probability the second source didn’t emit a signal, 1−q.

CAN YOU COVER THE GLOBE?ZACH WISSNER-GROSSAUGUST 28, 2020FIVETHIRTYEIGHT

When you were told that your opponent would “play rock or paper with equal probability,” most solvers assumed that meant both probabilities were 50 percent, rather than being equal but less than 50 percent.

CAN YOU REACH THE BEACH?ZACH WISSNER-GROSSAUGUST 7, 2020FIVETHIRTYEIGHT

SYNONYM OF THE DAY

OCTOBER 26, 1985

  • accidents
  • breaks
  • chances
  • crises
  • crossroads
  • emergencies
  • events
  • eventualities
  • exigencies
  • fortuities
  • happenings
  • if it's cools
  • incidents
  • junctures
  • likelihoods
  • occasions
  • odds
  • opportunities
  • passes
  • pinches
  • predicaments
  • probabilities
  • straits
  • turning points
  • uncertainties
  • zero hours

  • accident
  • break
  • chance
  • crisis
  • crossroads
  • emergency
  • event
  • eventuality
  • exigency
  • fortuity
  • happening
  • if it's cool
  • incident
  • juncture
  • likelihood
  • occasion
  • odds
  • opportunity
  • pass
  • pinch
  • predicament
  • probability
  • strait
  • turning point
  • uncertainty
  • zero hour

  • believability
  • chance
  • integrity
  • likelihood
  • plausibility
  • possibility
  • probability
  • prospect
  • reliability
  • satisfactoriness
  • solidity
  • solidness
  • soundness
  • tenability
  • trustworthiness
  • validity

  • clouds
  • crisis
  • double trouble
  • dynamite
  • emergency
  • endangerment
  • exigency
  • exposure
  • hot potato
  • insecurity
  • instability
  • jeopardy
  • menace
  • peril
  • pitfall
  • possibility
  • precariousness
  • precipice
  • probability
  • risk
  • risky business
  • slipperiness
  • storm
  • thin ice
  • threat
  • uncertainty
  • venture
  • vulnerability

  • clouds
  • crises
  • double troubles
  • dynamite
  • emergencies
  • endangerments
  • exigencies
  • exposures
  • hot potatos
  • insecurities
  • instabilities
  • jeopardy
  • menaces
  • perils
  • pitfalls
  • possibilities
  • precariousnesses
  • precipices
  • probabilities
  • risks
  • risky businesses
  • slipperiness
  • storms
  • thin ices
  • threats
  • uncertainties
  • ventures
  • vulnerabilities

  • aftereffect
  • aftermath
  • any case
  • case
  • chance
  • consequence
  • contingency
  • effect
  • event
  • goings-on
  • happening
  • issue
  • likelihood
  • outcome
  • possibility
  • probability
  • result
  • sequel
  • toss-up
  • upshot

Roget's 21st Century Thesaurus, Third Edition Copyright © 2013 by the Philip Lief Group.

Chance Events

Randomness is all around us. Probability theory is the mathematical framework that allows us to analyze chance events in a logically sound manner. The probability of an event is a number indicating how likely that event will occur. This number is always between 0 and 1, where 0 indicates impossibility and 1 indicates certainty.

A classic example of a probabilistic experiment is a fair coin toss, in which the two possible outcomes are heads or tails. In this case, the probability of flipping a head or a tail is 1/2. In an actual series of coin tosses, we may get more or less than exactly 50% heads. But as the number of flips increases, the long-run frequency of heads is bound to get closer and closer to 50%.

Flip the Coin

Flip 100 times

For an unfair or weighted coin, the two outcomes are not equally likely. You can change the weight or distribution of the coin by dragging the true probability bars (on the right in blue) up or down. If we assign numbers to the outcomes — say, 1 for heads, 0 for tails — then we have created the mathematical object known as a random variable.

Expectation

The expectation of a random variable is a number that attempts to capture the center of that random variable's distribution. It can be interpreted as the long-run average of many independent samples from the given distribution. More precisely, it is defined as the probability-weighted sum of all possible values in the random variable's support,

$$\text{E}[X] = \sum_{x \in \mathcal{X}}xP(x)$$

Consider the probabilistic experiment of rolling a fair die and watch as the running sample mean converges to the expectation of 3.5.

Roll the Die

Roll 100 times

Change the distribution of the different faces of the die (thus making the die biased or "unfair") by adjusting the blue bars below and observe how this changes the expectation.

Variance

Whereas expectation provides a measure of centrality, the variance of a random variable quantifies the spread of that random variable's distribution. The variance is the average value of the squared difference between the random variable and its expectation,

$$\text{Var}(X) = \text{E}[(X - \text{E}[X])^2]$$

Draw cards randomly from a deck of ten cards. As you continue drawing cards, observe that the running average of squared differences (in green) begins to resemble the true variance (in blue).

Draw a Card

Draw 100 times

Toggle which cards you want to include in the deck by clicking on them below.

What is probability?

Probability is simply how likely something is to happen. Whenever we’re unsure about the outcome of an event, we can talk about the probabilities of certain outcomes—how likely they are. The analysis of events governed by probability is called statistics.

What is the probability of an event happening?

The best we can say is how likely they are to happen, using the idea of probability. When a single die is thrown, there are six possible outcomes: 1, 2, 3, 4, 5, 6. Probability of an event happening = Number of ways it can happen Total number of outcomes Number of ways it can happen: 1 (there is only 1 face with a "4" on it)

How do you find the probability of a favorable outcome?

For an experiment having n number of outcomes, the number of favorable outcomes can be denoted by x. The formula to calculate the probability of an event is as follows. Probability (Event) = Favourable Outcomes/Total Outcomes = x/n

What is formula for probability?

Formula for Probability. The probability formula is defined as the possibility of an event to happen is equal to the ratio of the number of outcomes and the total number of outcomes. Sometimes students get mistaken for “favourable outcome” with “desirable outcome”.

What is probability explain?

A probability is a number that reflects the chance or likelihood that a particular event will occur. Probabilities can be expressed as proportions that range from 0 to 1, and they can also be expressed as percentages ranging from 0% to 100%.

How do you calculate probability?

The probability of any event depends upon the number of favorable outcomes and the total outcomes. In general, the probability is the ratio of the number of favorable outcomes to the total outcomes in that sample space. It is expressed as, Probability of an event P(E) = (Number of favorable outcomes) ÷ (Sample space).

What are the 4 types of probability?

Four perspectives on probability are commonly used: Classical, Empirical, Subjective, and Axiomatic.

What are the 3 rules of probability?

There are three main rules associated with basic probability: the addition rule, the multiplication rule, and the complement rule.