Stats - Mean | Olly Britton

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.