Surveying roaming dog populations: guidelines ... - Animal Sheltering

Annex 1
CONTENTS
Worked example:
From counts to population estimates with confidence intervals
The following worked example uses fictitious data to work through how you would use the results of
counts to estimate the roaming dog population of a city. It uses the example started in the ‘Selecting a
sample of blocks’ section of this document.
INTRODUCTION
COUNTING DOGS
Figure A1. Central Cairo divided into 108 blocks, with 27 blocks selected.
1. 27 blocks were selected as the sample from a total of 108 blocks (figure A1). Counting was carried
out over a three week period between the hours of 2am and 6am, as the street lighting in this area
was good and this was the period of time when the number of roaming dogs was at its highest. A
total of 542 dogs were seen in these 27 blocks.
Calculating the population estimate from the count:
2. The population estimate is calculated by dividing the total number of dogs counted in the sample
blocks by the sampling fraction:
total number of dogs counted
=
number of sample blocks
total number of blocks
542
27
108
=
542
0.25
= 2168
Between the hours of 2am and 6am there are an estimated 2,168 roaming dogs in this city.
MONITORING ONCE
CONCLUSIONS
17
ANNEXES