How do i calculate the standard deviation - Casio fx-300ES Calculator

For 1-Var statistics
Press [MODE][3:STAT] [1:1-VAR]. You are ready to enter values in the X column.
Enter a number and press [=]. Cursor jumps to second number to enter.
Keep entering numbers and pressing [=] till all numbers are in. Press the [=] key after the last one.
Press [AC] key to clear the screen.
Press [SHIFT] [STAT] (above digit 1.) then [5:Var]. Screen displays the statistical variables 1:n ;2: x bar; 3: x sigma n; 4:x sigma n-1.
Press the number corresponding to Referable you want, ex 1:n . The variable appears on screen. Press [=] and it will be displayed.
To display another variable press [SHIFT][STAT][5:Var][ 1,2, 3, or 4] .

To access the sum of squares sigma x^2 and the sum of data sigma x press[SHIFT][STAT][4:SUM] then [1: for sigma x^2] or [2: for sigma x]. Press [SHIFT][STAT][6:MinMax] to access minX and maxX.

For 2-var statistics
To perform 2 variable statistics you press [MODE][3:STAT] and any of the other regression options (except 1:1-Var). A two column template opens where you enter the X and Y values. When finished entering data, press [SHIFT][STAT][5:Var]. to access the different statistics. you should be able to recognize what each variable means.