HP 35s Scientific Calculator - Manual (Page 320)

C-12 ALG: Summary
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. 
If you wish to delete the incorrect values that were just entered, press z 4 .
After deleting the incorrect statistical data, the calculator will display the last
statistical data entered in line 1 (top line of the display) and value of n in line 2. If
there are no statistical data, the calculator will display n=0 in line 2.
Example:
After keying in the x, y–values on the left, make the corrections shown on the right:
Initial x, y Corrected x, y
20, 4 20, 5
400, 6 40, 6
Keys: Display: Description:
{ (4Σ)
Clears existing statistical data.
Z
6 
Σ-
)
Enters the first new data pair.
Z
6

Σ-
)
Display shows n, the number of data
pairs you entered.
{ Ž  !º

)
Brings back last x–value. Last y is still
in Y–register.
z 4 
Σ.
)
Deletes the last data pair.
Z
6 
Σ-
)
Reenters the last data pair.
Z
z
4

Σ.
)
Deletes the first data pair.
Z
6

Σ-
)
Reenters the first data pair. There is
still a total of two data pairs in the
statistics registers.