Section 6: Functions continue100
  4. The square of the number in the Y-register is added to the contents of the fourth statistical storage register (presently defined as R14).
  5. The number in the X-register is multiplied by the number in the Y-register, and the product is added to the contents of the fifth statistical storage register (presently defined as R15).
  6. The number 1 is added to the contents of the last statistical register (now defined as R16). After all of the above steps are performed by the calculator, the total number in the last register is placed into the display and the X-register.
When you execute Σ+ , the stack and statistical storage register contents are changed...
  ...from this... this.
T  t
R11  0.0000      
T  t
R11  Σx
Z  z
R12  0.0000      
Z  z
R12  Σx2
Y  y
R13  0.0000      
Y  y
R13  Σy
X  x
R14  0.0000      
X  n
R14  Σy2
R15  0.0000      
R15  Σx y
X  0.0000
R16  0.0000     LAST 
X  x
R16  n
To use any of the summations individually at any time, you can recall the contents of a statistical storage register into the X-register by pressing RCL and the register address. Or you can recall the contents of the desired storage register into just the display by pressing g VIEW followed by the statistical register address. Remember that VIEW does not disturb the stack registers.
When execution of Σ+ or Σ– causes the contents of any of the statistics register to exceed 9.999999999 × 1099, execution of the function is completed, the contents of all of the statistics registers are updated, and 9.999999999 × 1099 is placed in the register or registers that overflowed.
Example: Find Σx, Σx2, Σy, Σy2, and Σxy for the paired values of x and y listed below.
  7 5 9  
  5 3 8  
Keystrokes Display    
g CLΣ 
  Clears the statistical registers (presently R11 through R16).
5 Σ+ 
  First pair is accumulated, n = 1.
3 Σ+ 
  Second pair is accumulated; n = 2.