# Stats - Probability

> Source: https://ollybritton.com/notes/a-level/maths/topics/stats/probability/ · Updated: 2021-01-12 · Tags: stats, probability, year-1, school

##### What two forms do you give answers to probability questions??
* Decimals
* Fractions

##### What does $P(\text{experiment})$ mean??
The probability of experiment.

##### In terms of probability, what is an experiment??
A repeatable process that gives rise to a number of outcomes.

##### In terms of probability, what is an event??
A set of one or more outcomes.

##### What is sample space??
The set of all possible outcomes.

### 2021-01-21
##### What does it mean for two events to be mutually exclusive??
The two events can't happen at the same time.

##### If $A$ and $B$ are mutually exclusive, what is $P(A \text{and} B)$??
$$
0
$$

##### If $A$ and $B$ are mutually exclusive, what is $P(A \text{or} B)$??
$$
P(A) + P(B)
$$

##### What would the Venn diagram look like for two mutually exclusive events, $A$ and $B$??
![PHOTO MUTUALLY EXCLUSIVE VENN DIAGRAM](mutually-exclusive-venn-diagram.png)

##### What does it mean if two events are independent??
One event happening does not affect the probability of the other happening.

##### If $A$ and $B$ are independent, what is the probability of $P(A\text{and}B)$??
$$
P(A) \times P(B)
$$

##### Do mutually exclusive events overlap on a Venn diagram??
No.

##### Do independent events overlap on a Venn diagram??
Yes.

##### How could you prove mathematically that two events $A$ and $B$ aren't independent??
Show

$$
P(A \text{and} B) \neq P(A)\times P(B)
$$

### 2021-02-04
##### In an experiment calculating the percentage of left-handed people, what would you say instead of right-handed??
Not left handed.

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