Appendix IV - Survey Methodology

Survey Analysis
One general data analysis issue with many surveys is how to deal with “outliers,” which are individual responses that tend to inflate estimated averages and totals because they are particularly large. In order to err on the conservative side we chose to exclude such outliers when a single outlier expanded estimates by 50 percent or more. The other typical survey issue involves item non-responses, which are instances in which a questionnaire is completed but one or more questions (i.e., items) are not answered. In these cases, averages were calculated omitting the non-responses.

In order to take advantage of visit-related responses from both the household telephone and online surveys, we usually combined estimates from the two surveys by weighting estimates by respective number of responses. For example, the estimated average time to use alternatives was 94.5 minutes for the online survey and 73.5 minutes for the telephone survey. Using the weights calculated for that question, we arrive at a combine average of 84 minutes (i.e., 94.5 × 0.58 + $73.5 × 0.42).

Some survey questions required respondents to check a range of values. For example, we asked for annual household income in ranges of under $30,000, between $30,000 and $50,000, between $50,000 and $75,000, between $75,000 and $100,000 and more than $100,000. In some instances we needed to estimate an average salary from these responses. If the proportion of responses for the ranges is about equal one could use the mid-points and multiply each range mid-point by the proportion of responses to that range and sum the products across the ranges. However, these values are often skewed in a log-normal manner, in which case a geometric average is used in lieu of a mid-point. This average is the square root of the product of the range points; for example, the square root of $25,000 times $50,000 or $35,355. The outside values for the end ranges are approximated from examining the log-normal plots.

To establish an hourly rate, for example to apply to the number of hours spent for work-related purposes in the library, we added a 25 percent fringe benefit rate to personal annual income and divided by 2,080 annual hours. Both of these values yield conservative estimates.

Adult users in the online survey were asked questions about taxes that are designated for public libraries and, on both library user surveys, adults were asked how much they would be willing to accept and pay for their library card. In fact, adult residents average paying about $42 per adult in local taxes and $47 per adult when state and federal tax contributions are included. When asked: “If someone would buy your public library card each year, how much would you ask for it?”. Fifty-six percent of combined survey respondents said they would not give it up. Nearly 45 percent of telephone respondents said they would accept less than they pay in taxes, but the rest indicated that they would only accept more than what they pay in taxes. They were also asked: “If you paid a price for your library card each year instead of paying taxes, how much would you be willing to pay for it?”. The average amount they said they were willing to pay was, in fact, less than the amount they pay and could demonstrate the impact of the economic downturn on individuals’ feelings of wealth. But adult users still demonstrate that they are willing to pay many times that amount over a year considering their time and other costs spent using their public library.

Online respondents tended to skip questions, particularly those requesting demographic information. Where appropriate, telephone survey demographic responses were used instead.