The National Crop Loss Assessment Network (NCLAN) began in 1980 to coordinate research on the impact of ozone (O3) on agricultural crops. During a 7‐yr period, the program investigated 14 crops at sites across the country in a total of 41 studies. A major objective was to develop dose‐response relationships between yield of major agricultural crop species and ozone pollution in order to estimate the economic impact of ozone pollution. This paper outlines the statistical methodologies used in combining the dose‐response information for each species over all NCLAN studies, and summarizes the ozone dose‐response relationships obtained. Differences in experimental designs, treatment combinations, and levels of ozone across studies invalidated the conventional analysis of variance approach to combining information across studies. Regression analyses, with weighted least squares and transformations as needed, were used. Dose‐response relationships between yield and ozone were quantified with the nonlinear Weibull response equation and with confidence interval estimates of percentage yield losses. Significant yield losses from ozone were found for 13 of 14 crops studied. The nature of the yield response to ozone differed among crops with soybean [Glycine max (L.) Merr.] being the most sensitive and showing a nearly linear response. Losses from ozone at 0.06 μL L−1 compared with 0.025 μL L−1 were estimated as high as 20%. The impact of ozone was shown to be affected by level of moisture stress but not by SO2.
The effect of personalization on mail survey response rates was examined in nine studies that included 17 comparisons under several research conditions. A study of this variable across multiple experiments in five agricultural experiment stations was undertaken because of conflicting results from previous research and from concern that the effectiveness of personalization might have decreased over time. Results show that, while response to general public surveys appeared to increase modestly across all treatment groups, there was no positive effect for populations in which a group identity (e.g., Dear Oregon Gardner or Dear ATV Owner) is employed to address respondents in cover letters. Personalization appears to remain useful for improving response in surveys of the general public.
Telephone surveys have been a ubiquitous method of collecting survey data, but the environment for telephone surveys is changing. Many surveys are transitioning from telephone to self-administration or combinations of modes for both recruitment and survey administration. Survey organizations are conducting these transitions from telephone to mixed modes with only limited guidance from existing empirical literature and best practices. This article summarizes findings by an AAPOR Task Force on how these transitions have occurred for surveys and research organizations in general. We find that transitions from a telephone to a self-administered or mixed-mode survey are motivated by a desire to control costs, to maintain or improve data quality, or both. The most common mode to recruit respondents when transitioning is mail, but recent mixed-mode studies use only web or mail and web together as survey administration modes. Although early studies found that telephone response rates met or exceeded response rates to the self-administered or mixed modes, after about 2013, response rates to the self-administered or mixed modes tended to exceed those for the telephone mode, largely because of a decline in the telephone mode response rates. Transitioning offers opportunities related to improved frame coverage and geographic targeting, delivery of incentives, visual design of an instrument, and cost savings, but challenges exist related to selecting a respondent within a household, length of a questionnaire, differences across modes in use of computerization to facilitate skip patterns and other questionnaire design features, and lack of an interviewer for respondent motivation and clarification. Other challenges related to surveying youth, conducting surveys in multiple languages, collecting nonsurvey data such as biomeasures or consent to link to administrative data, and estimation with multiple modes are also prominent.
Although surfers have high incidental exposure to marine waters, no studies have investigated if surfer risk behaviors (such as surfing during advisories, near an outfall, during a rain event, or use of personal protective equipment) increase or decrease the risk of acquiring waterborne illnesses. We used a web-based survey to assess the association between risk-based behaviors and self-reported illnesses among Pacific Northwest surfers. Commonly reported illnesses include: ear infection or discharge (38%), sore throat or a cough (28%), diarrhea (16%), fever (10.5%), and vomiting (7%). Surfing often during rain events was associated with an increased likelihood of diarrhea (OR = 2.7; 95% CI: 1.4-5.47), sore throat (OR = 1.26; 95% CI: 1.01-2.05), and ear infection (OR = 1.39; 95% CI: 1.01-2.32). Surfing during a health advisory was associated with increased likelihood of diarrhea (OR = 1.94; 95% CI: 1.03-4.64) and sore throat (OR = 2.32; 95% CI: 1.23-4.40). Other behaviors associated with increased illnesses include body surfing, surfing near an outfall, frequency of surfing, and use of ear plugs. Approximately 40% of surfers were unaware if they had surfed during an active health advisory and 29% knowingly surfed during advisories, suggesting the need to engage this population about potential harm and behaviors that may increase health risk.
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