Praxis Core Math
- Data representations | Lesson
- Data representations | Worked example
- Center and spread | Lesson
- Center and spread | Worked example
- Random sampling | Lesson
- Random sampling | Worked example
- Scatterplots | Lesson
- Scatterplots | Worked example
- Interpreting linear models | Lesson
- Interpreting linear models | Worked example
- Correlation and Causation | Lesson
- Correlation and causation | Worked example
- Probability | Lesson
- Probability | Worked example
What is a probability?
A probability indicates the chance that an
A probability can be any number from to .
- A probability of or means that an event will never happen.
- A probability of or means that an event is equally likely to happen or not happen.
- A probability of or means that an event will certainly happen.
The probability that event will happen is written as .
The probability that event will not happen, , is equal to .
What skills are tested?
- Calculating the probability that an event will happen (or will not happen) based on a description of the situation
- Calculating the probability that an event will happen (or will not happen) based on information in a data display
- Calculating a count or quantity from a probability
- Comparing probabilities or drawing conclusions based on probabilities
How is the probability of an event calculated?
An event could be the outcome of any random process such as the toss of a fair coin, the roll of a fair number cube, or the random selection of an item from a group.
We use the notation to represent "the probability that event will happen".
How is the probability of an event calculated using information in a data display?
When calculating the probability that a randomly selected item will have certain attribute(s), the information we need may be in a data display.
In such cases,
- The ways can happen is the number of items of type .
- The number of possible outcomes is the total number in the group.
How can we calculate a count or quantity from a probability?
Sometimes we are given the probability and are asked to calculate either the number of possible outcomes or the number of ways can happen
To solve these questions:
- Substitute known values into the equation .
- Solve for the unknown quantity.
TRY: CALCULATING A PROBABILTY
A box contains red, green, and orange candies. If one candy is selected randomly from the box, what is the probability that the selected candy will be red?
TRY: CALCULATING A QUANTITY FROM A PROBABILITY
A gumball machine contains red, blue, and green gumballs. There are red gumballs and blue gumballs. When the handle of the machine is turned, one gumball is randomly dispensed. If the probability of getting a red gumball is , how many green gumballs are in the machine?
TRY: COMPARING PROBABILITIES
|Doughnut Variety||Number of Doughnuts|
The table above shows the number of doughnuts in a bakery display case by variety. If a doughnut is chosen at random from the display case, which of the following statements is true?
TRY: CALCULATING A PROBABILITY USING A TABLE
The table above shows data about the passengers aboard the Titanic. If a passenger who traveled on the Titanic is selected at random, what is the probability that the selected passenger was someone who traveled in first class?
Round your answer the nearest integer.
Things to remember
A probability indicates the chance that an event will happen.
A probability can be any number between and .
The probability that event A will happen is:
The probability that event A will not happen is: