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Table 3 Advantages and disadvantages of four different collection methods that were used in the seven studies included in the final analysis of a systematic review examining methods to estimate owned dog and cat populations

From: Methods used to estimate the size of the owned cat and dog population: a systematic review

Data collection method used to determine pet population estimate Studies Advantages Disadvantages
Mail out survey using a commercial list of contacts AVMA [1, 36] Reduces bias towards wealthier participants associated with telephone surveys. Selection bias introduced as households that are not on the commercial list are excluded. May introduce measurement bias as the participant will be aware what the study is about.
Overestimation of population may be introduced as a period prevalence is measured in these studies.
Door to door survey Butler and Bingham [19] Reduces non-response. Costly and time consuming, probably only feasible in a small study area.
Selection bias may have been introduced as only houses that were within 500 meters of a road were included and only roads that were passable by vehicle were used. Also true random selection was not used.
Ortega-Pacheco et al. [51] Costly and time consuming, probably only feasible in a small study area.
Selection bias may have been introduced in this study as only households with a telephone could be included, this may have led to households with a higher SEC being over represented. Random selection was not used in the door to door surveys.
Random-digit dialled telephone survey Lengerich et al. [47] Ortega-Pacheco et al. [51] Cost effective and logistically allows a large number of participants to be recruited in a short period of time. Large numbers of non-domestic based numbers may be included leading to greater non-response.
Selection bias may have been introduced in this study as only households with a telephone could be included; this may have led to households with a higher social economic class (SEC) being over-represented.
Randomised telephone survey using a list of numbers Slater et al. [5] Cost effective and logistically allows a large number of participants to be recruited in a short period of time. Reduces number of non-household based numbers associated with random digit dial surveys. Selection bias may have been introduced in this study as only households with a telephone could be included, and if the telephone number was not listed it could not be included.
An explanation of the study was given at the start of the interview, which may lead to measurement bias as households with pets might be more likely to complete the questionnaire.
Murray et al. [3] Selection bias may have been introduced in this study as only households with a telephone could be included, and if the telephone number was not listed it could not be included.