# Stats - Mean

> Source: https://ollybritton.com/notes/a-level/maths/topics/stats/mean/ · Updated: 2020-09-10 · Tags: stats, year-1

# Mean
The mean is the average value. In stats, it is written as $\bar{x}$ where $x$ is the data.

##### What does $\bar{x}$ mean??
The mean of the values in $x$.

##### What is the notation for the mean of the values in $x$??
$\bar{x}$.

##### What is the formula for mean??
$$
\bar{x} = \frac{\sum x}{n}
$$

##### What does $\sum x$ mean??
The sum of the values in $x$.

##### What is the formula for mean for frequency data??
$$
\bar{x} = \frac{\sum f x}{\sum f}
$$

##### What does $\sum f x$ mean??
The sum of all (frequencies multiplied by their values).

##### What does $\sum f$ mean??
The sum of all frequencies.

##### How can you deal with intervals for frequency tables??
Use the midpoint of the interval.

##### How could you represent $0 \leq h < 0.5$??
$0.25$

##### If the mean of class $A$ is $62$ and the mean of class $B$ is $75$, how could you calculate the combined mean??
$$
\frac{20 \times 62 + 30 \times 75}{20 + 30}
$$

##### Finding the combined mean is a special case of??
Finding the mean in a frequency table.

#####

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