The Quick Count and Election Observation

THE QUICK COUNT AND ELECTION OBSERVATION
The case of a quick count conducted during the 2001 Peruvian presidential
elections can illustrate the above steps:
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The size of the total relevant population (number of eligible voters) in
Peru was 14,570,774. The population was assumed to be heterogeneous—the
race between two candidates was expected to be close,
so the level of homogeneity of the population was set at 50 percent
(0.5). A margin of error of 0.32 percent and a confidence level of 99
percent were selected. For the purposed of making a calculation, the
proportion of homogeneity was expressed as a value with a range
between 0 and 1, as was the margin of error. The expected level of
homogeneity was set as 50 percent, the most conservative assumption;
it is expressed as 0.5 in the formula, and the margin of error of
0.32 percent (out of a possible 100 percent) is expressed as .0032.
These values were plugged into the formula as follows.
N =
.50 (1-.50)
(.0032) 2 .50 (1-.50)
(2.58) 2 +
14,570,774
=
.000010
6.6564
+
.25
.25
14,570,774
=
.25
.000001515 + .000000017
=
.25
.000001532
= 163,185
At this point, analysts know how many voters have to be consulted. However,
the units of analysis are not individual voters; they are polling stations.
Therefore, the next step is to determine how many polling stations must be
selected to represent the required number of voters. The Peruvian calculation
can be continued to illustrate the point:
On average, there were approximately 160 voters per polling station
in Peru. Therefore, the sample size of 163,185 (eligible voters) was
divided by the number of electors per station (160) to determine the
number of polling stations in our sample (1,020). Consequently, the
sample size for the 2001 Peru quick count was 1,020 polling stations.