HP 33s - Manual (Page 146)

11–2 Statistical Operations
Entering One–Variable Data
1. Press { c { Σ} to clear existing statistical data.
2. Key in each x–value and press  .
3. The display shows n, the number of statistical data values now accumulated.
Pressing  actually enters two variables into the statistics registers because the
value already in the Y–register is accumulated as the y–value. For this reason, the
calculator will perform linear regression and show you values based on y even
when you have entered only x–data — or even if you have entered an unequal
number of x–and y–values. No error occurs, but the results are obviously not
meaningful.
To recall a value to the display immediately after it has been entered, press {
 .
Entering Two–Variable Data
In RPN mode, when your data consist of two variables, x is the independent
variable
and y is the dependent variable. Remember to enter an (x, y) pair in
reverse order (y ‘ x ) so that y ends up in the Y–register and X in the
X–register.
1. Press { c { Σ} to clear existing statistical data.
2. Key in the y–value first and press ‘ .
3. Key in the corresponding x–value and press  .
4. The display shows n, the number of statistical data pairs you have
accumulated.
5. Continue entering x , y–pairs. n is updated with each entry.
To recall an x–value to the display immediately after it has been entered, press
{  .
Correcting Errors in Data Entry
If you make a mistake when entering statistical data, delete the incorrect data and
add the correct data. Even if only one value of an x, y–pair is incorrect, you must
delete and reenter both values.
To correct statistical data: