planning a governance assessment - United Nations Development ...

Examples of sampling error rates at 95 percent certainty
A sample size of:
Give you a margin
of error of around:
2500 +/- 2.0 %
1500 +/- 2.5 %
1000 +/- 3.1 %
500 +/- 4.4 %
200 +/- 6.9 %
100 +/- 9.8 %
50 +/- 13.9 %
Costs and benefits concerning sampling and sample size
In conclusion, large samples cost more money, but offer more precision (better estimates). Probability sampling, which is
usually more expensive, is preferred over non-probability sampling. However, in some cases non-probability sampling can
work quite well and is used all over the world in large and small projects. If one is seeking the opinions of experts, then
non-probability sampling is something to consider. Most of the time, the size of the sample is driven by how much money
is available – more money, larger sample. The larger the sample, the more precise the estimates become and the easier it
is to examine differences between groups in society. However, there is a point where the amount of precision gained by
increasing the sample size diminishes. This means that even if resources are plentiful, there is no reason for excessively large
sample sizes (see the examples offered above).
When it comes to designing and drawing large representative samples, clearly NSOs have the experience and also may offer
significant cost advantages. However, if the project is going to attempt to reach vulnerable populations such as domestics,
homeless or displaced people, even NSOs may need to modify their “normal” sampling procedures. Getting to these hard to
reach populations may require more time and money.
Generally, it is better to have a well-executed study with a smaller sample, than a less rigorous study with a larger sample.
Besides the costs associated with larger samples, you must also factor in the costs of designing, drawing (selecting the
respondents) and managing the sample. If examining various groups in the population is a priority, then it would be wise to
allocate sufficient funds for a sample large enough (with an acceptable MOE) to allow for disaggregation of the data.
Planning a Governance Assessment: A Guide to Approaches, Costs and Benefits
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