The Quick Count and Election Observation
The Quick Count and Election Observation
The Quick Count and Election Observation
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THE QUICK COUNT AND ELECTION OBSERVATION<br />
attributable to the role of the sample size in constructing the margin of error.<br />
Recall that the formula for margin of error is:<br />
77<br />
(Assumed heterogeneity) * (z value at chosen confidence level)<br />
√n<br />
<strong>The</strong> fact is that variations in the size of polling station will also affect the ‘n.’<br />
VOTERS POLLING STATIONS<br />
If station size<br />
is 160<br />
If station size<br />
is 200<br />
If station size<br />
is 500<br />
Sample 163,185 1,020 816 324<br />
FIGURE 5-5:<br />
SAMPLE SIZE AND MARGINS<br />
OF ERROR<br />
Margin of error<br />
(95% confidence level)<br />
Margin of error<br />
(99% confidence level)<br />
±0.24 ±3.01 ±3.43 ±5.4<br />
±0.32 ±4.03 ±4.5 ±7.1<br />
Notice that the margin of error depends on the number of polling stations in<br />
the sample. If the polling stations are large, fewer of them are needed to generate<br />
the desired sample of 163,185 voters. <strong>The</strong> margin of error calculated for<br />
the polling stations is larger than the margin of error calculated for the sample<br />
of voters. <strong>The</strong> resulting margin of error for quick counts falls somewhere<br />
in between the lower <strong>and</strong> higher margin of error.<br />
Tracking the changes to the margin of error for a range of polling station sizes<br />
shows that, as the number of stations needed to form a sample of voters<br />
decreases, the margin of error increases. Figure 5-6 illustrates the relationship<br />
between the size of the polling station <strong>and</strong> the margin of error.<br />
As the number of stations<br />
need to form a<br />
sample of voters<br />
decreases, the margin<br />
of error increases.<br />
VOTERS/<br />
STATION<br />
# STATIONS TO<br />
GET SAMPLE<br />
MARGIN OF ERROR<br />
(confidence levels)<br />
FIGURE 5-6:<br />
POLLING STATION SIZE<br />
AND MARGIN OF ERROR<br />
95% 99%<br />
150 1,088 ±2.97 ±3.91<br />
200 816 ±3.43 ±4.52<br />
250 653 ±3.84 ±5.05<br />
300 544 ±4.20 ±5.53<br />
350 466 ±4.54 ±5.97<br />
400 408 ±4.85 ±6.39<br />
450 363 ±5.14 ±6.77<br />
500 327 ±5.42 ±7.13