These **numerous statistical resources (calculators, quizzes, games, exercises, reminders, formulas) provide tools for practicing statistics**.

- Standard deviation calculator : standard_deviation. Calculate online the standard deviation of a set of values, the exact result is given to the calculation steps.
- Max of a list : max. The max function returns the greatest value of a list.
- Min of a set of number : min. The min function returns the smallest value of a set of numbers.
- Arithmetic mean : average. The average function allows to calculate the arithmetic mean of a series of values.
- Variance : variance. The variance function allows to calculate online the variance of a serie.

- Quiz on statistics : This statistical calculations quiz allows you to practice calculating the mean and frequency of a series.

For any series`(x_1, ..., x_n)` of real numbers, we define its **arithmetic mean by the formula** : `bar x= 1/n sum_(i=1)^n x_i`

So to calculate the **average** of several values, we add all the values and divide the result by the number of values.

Using this formula, for example, we can calculate the quarterly average for a student who got 13; 16; 7 and 12 on his math homework.

To calculate the **weighted average** of a statistical series defined by giving the pairs `(x_i;n_i)`, where `x_i` is the value of the characteristic under study and `n_i` is the number of that value, `i in NN`, `1<=i<=p`,
we use the formula : `bar x= (sum_(i=1)^n x_i*n_i)/(sum_(i=1)^n n_i)=(n_1*x_1+n_2*x_2+...+x_p)/(n_1+n_2+...+n_p)`

Using this formula, it is for example possible to calculate the weighted average of a student who got 16 in French (coefficient 3), 11 in English (coefficient 2), 12 in mathematics (coefficient 5).

The **frequency** of a data is the quotient obtained by dividing the number of this data by the total number.

F=`"number"/"total number"`

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