Guidelines for Developing and Evaluating Tree Ordinances

Public polling


Evaluating public attitudes and knowledge about trees and urban forest management.

Materials needed:

Varies with the type of survey being conducted. See discussion below.


The use of polling or surveying to assess public opinions, attitudes, beliefs, and knowledge is well known to most people. On almost any day, the news media report on the results of a poll or survey on some pressing topic. Polling can be useful in assessing the knowledge and attitudes of the community with respect to urban forestry issues. Properly designed polls can also be used to evaluate whether an ordinance, educational program, or other management activity has brought about changes in knowledge, attitudes, and practices in the community. Information is normally gathered from the public either through interviews or self-completed questionnaires.


Compared with questionnaires, interviews generally have greater flexibility, tend to elicit a higher response rate, and allow for more precise selection of respondents. However, persons conducting interviews need to be carefully trained to avoid introducing bias into the data.

Interviews may be conducted either in person or by telephone. Telephone interviews are less expensive to conduct, allow for better sampling designs, and can be used in conjunction with computers. Computer-assisted telephone interviewing (CATI) systems are available and can increase the efficiency of telephone interviews. A CATI system can be used to help the interviewer adjust their questions based on information obtained during the interview, and allows for the direct entry of data as the interview proceeds.

Self-completed questionnaires

Self-completed questionnaires have the advantage of being easier to administer than interviews. Questionnaires are most commonly sent and returned by mail. Respondents have more opportunity to think about questions or look up information for a self-completed questionnaire than in an interview. While it is now possible to set up questionnaires that would be accessed via the Internet, the sample responding to an Internet survey may not be especially representative of the population as a whole or even of the portion of the population that uses the Internet.

Typically, prior to the main survey mailing, the questionnaire is pretested on a small sample. Any problems that are identified in the construction of the questionnaire can then be corrected.

Several techniques are commonly employed to boost the return rate for mail surveys. These include the use of advance notification, attractive first-class stamps rather than bulk postage, hand addressing, postage-paid return envelopes, carefully-timed reminder postcards, and repeat mailings of the questionnaire to nonrespondents. Token incentives included with the survey are sometimes used to increase the return rate, but these will also increase survey costs. Incentives may also introduce bias into the returns if they tend to motivate some groups more than others.

Survey design considerations

Much of the difference in cost between the various methods is related to the logistics of data collection, since design and analysis costs will be similar. In-person interviews are generally the most costly and complex surveys to conduct, due to the logistics of traveling door-to-door. The cost of telephone surveys will vary with the length and complexity of the survey and the sample size. Costs of the mail survey vary with the size of the mailing and the number of follow-up mailings used.

Good survey design and sampling technique are critical to the success of sample surveys conducted by any method. Care must also be taken in the data collection and entry process, to avoid introducing errors. Finally, even a well-conducted survey will not yield meaningful results if data analysis and interpretation are flawed. Thus, while the concepts behind public polling are reasonably straightforward, there is a fair amount of art and science involved in conducting a useful study. Gross design and execution errors can lead to meaningless or misleading results. More subtle errors may not completely invalidate survey results, but can decrease the reliability of the study.

If you are interested in conducting a public survey but lack the necessary technical background or resources, there are various sources of assistance available. Survey research units are associated with a number of state college and university campuses. Some of these units,can contract with cities or counties to design or conduct surveys. Others may provide information or assist in studies on a cooperative basis. In addition, a number of private firms specialize in conducting public surveys primarily for market research. The scope of services provided and quality of work performed by these or other consulting firms can vary widely, so careful shopping is advised.

Sampling considerations for public polling

For all but the very smallest municipalities, assessments of citizen attitudes and knowledge will be based on polling a representative sample of the total population. While most of the points noted under Sampling from Populations apply, demographic factors also need to be considered to avoid bias in the study design. For instance, Sommer et al (1990) found that compared to younger citizens, older citizens were more likely to have negative opinions about street trees in front of their homes. It may be desirable to account for differences due to age, sex, sociological, or other demographic factors in the survey. Such information may help local governments decide whether education or other programs need to be targeted toward certain segments of the population.