Probability & Relative Frequency
Probability measures how likely events are. Experimental probability comes from trials; theoretical probability is calculated mathematically.
What You Need to Know
Key Concept Diagram
Theoretical P(event) = favourable outcomes ÷ total equally likely outcomes
Relative (experimental) frequency = number of successes ÷ number of trials
As trial number increases, experimental probability approaches theoretical probability
Complementary events: P(event) + P(not event) = 1
Key Vocabulary
Trial
One experiment or observation in a probability experiment
Sample space
The set of all possible outcomes
Relative frequency
Experimental probability based on actual results
Complementary event
The event of something NOT happening
Knowledge Check
Select the correct answer for each question. Click "Check Answer" to see if you are right.
Question 1
A bag has 3 red and 7 blue balls. What is the theoretical probability of picking red?
Question 2
In 100 coin flips, heads appeared 53 times. What is the relative frequency of heads?
Question 3
If P(rain tomorrow) = 0.3, what is P(no rain tomorrow)?
Key Concepts Summary
- ●Theoretical P(event) = favourable outcomes ÷ total equally likely outcomes
- ●Relative (experimental) frequency = number of successes ÷ number of trials
- ●As trial number increases, experimental probability approaches theoretical probability
- ●Complementary events: P(event) + P(not event) = 1