Formulas: data and probability, grade 7

Relative frequency

The relative frequency of a value – $\displaystyle f$ its frequency, $\displaystyle n$ the number of all the data
$\displaystyle \frac{f}{n}$
The relative frequencies of all the values add up to 1
$\displaystyle \frac{f_1}{n}+\frac{f_2}{n}+\dots+\frac{f_k}{n}=1$

Estimating the probability of an event $\displaystyle A$ – $\displaystyle f$ how many times it happened, $\displaystyle n$ how many times the experiment was done
$\displaystyle P(A)\approx\frac{f}{n}$
A probability is a number from 0 to 1 – an impossible event 0, a certain event 1
$\displaystyle 0\le P(A)\le1$
How many times the event is expected to happen in $\displaystyle n$ experiments
$\displaystyle P(A)\cdot n$