City Services Satisfaction Survey 2019 City Services Satisfaction Survey | Page 9

Statistical Variation
Statistical Variation
All numbers and percentages shown in this report are subject to sampling variation or statistical
error. The smaller the sample of respondents is (i.e., the smaller the “base”), the larger the
statistical error in the corresponding numbers or percentages. The table below presents
approximate statistical-error ranges, as a function of sample size, at a 95% confidence level.
Maximum Statistical Error
(At Various Percentage Levels)
Sample
Size
50
75
100
150
200
250
300
50%
±14.0
±11.4
±9.8
±8.0
±6.9
±6.2
±5.6
40% or
60%
±13.7
±11.1
±9.6
±7.8
±6.8
±6.1
±5.5
30% or
70%
±12.8
±10.4
±9.0
±7.3
±6.3
±5.7
±5.2
20% or
80%
±11.2
±9.1
±7.9
±6.4
±5.5
±4.9
±4.5
10% or
90%
±8.3
±6.8
±5.9
±4.8
±4.2
±3.7
±3.4
Caution should be used when interpreting results with a base size smaller than 100 respondents. Throughout this report, any small base sizes will
be indicated with an exclamation point (!).
Copyright © 2020 Decision Analyst 
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