Apple iWork '09 - Manual (Page 364)

Function and arguments Description of result
=COVAR(B2:B11, C2:C11) Determines the covariance of question 1 and
question 2. Covariance is a measure of how
much two variables (in this case, answers to
survey questions) change together. Specifically,
this would look at the question: If a respondent
answered question 1 with a higher (or lower)
value than the average for question 1, did the
respondent also answer question 2 with a higher
(or lower) value than the average for question 2?
Note: COVAR would not work with the table
using a scale of A–E, as it requires numeric
arguments.
=STDEV(B2:B11) or =STDEVP(B2:B11) Determines the standard deviation, one measure
of dispersion, of the answers to question 1. If
you extend this formula across the row, you
would see that the answers to question 3 had
the highest standard deviation. If the results
represented responses from the entire population
being studied, rather than a sample, STDEVP
would be used instead of STDEV. Note that STDEV
is the square root of VAR.
=VAR(B2:B11) or =VARP(B2:B11) Determines the variance, one measure of
dispersion, of the answers to question 1. If you
extended this formula across the row, you would
see that the answers to question 5 had the lowest
variance. If the results represented responses
from the entire population being studied, rather
than a sample, VARP would be used instead of
VAR. Note that VAR is the square of STDEV.
364 Chapter 13 Additional Examples and Topics