HP 32SII - Manual (Page 159)

Statistical Operations 11–11
File name 32sii-Manual-E-0424
Printed Date : 2003/4/24 Size : 17.7 x 25.2 cm
Normalizing Close, Large Numbers
The calculator might be unable to correctly calculate the standard deviation
and linear regression for a variable whose data values differ by a relatively
small amount. To avoid this, normalize the data by entering each value as the
difference from one central value (such as the mean). For normalized
x–values, this difference must then be added back to the calculation of
x
and xˆ , and
yˆ
and b roust also be adjusted. For example, if your x–values
were 7776999, 7777000, and 7777001, you should enter the data as –1,
0, and 1; then add 7777000 back to
x and xˆ . For b, add back
7777000 × m. To calculate
yˆ
, be sure to supply an x–value that is less
7777000.
Similar inaccuracies can result if your x and y values have greatly different
magnitudes. Again, scaling the data can avoid this problem.
Effect of Deleted Data
Executing z 4 does not delete any rounding errors that might have been
generated in the statistics registers by the original data values. This difference
is not serious unless the incorrect data have a magnitude that is enormous
compared with the correct data; in such a case, it would be wise to clear and
reenter all the data.
Summation Values and the Statistics Registers
The statistics registers are six unique locations in memory that store the
accumulation of the six summation values.
Summation Statistics
Pressing { 5 gives you access to the contents of the statistics
registers:
Press { Q } to recall the number of accumulated data sets.
Press { º } to recall the sum of the x–values.
Press { ¸ } to recall the sum of the y–values.