National Survey of Fishing, Hunting, and Wildlife ... - All About Birds

lation 6 to 15 years of age were derivedfrom the screening interview. Statisticsfor the population 16 years old andolder come from both the screeningand detailed interviews. Estimates thatcome from the screening sample arepresented in Appendix B.A. Screening SampleEvery interviewed person inthe screening sample receiveda screening weight that was theproduct of the following factors:1. Base Weight. The base weightis the inverse of the household’sprobability of selection.2 Household NoninterviewAdjustment. The noninterviewadjustment inflates the weightassigned to interiewed householdsto account for householdseligible for interview butfor which no interview wasobtained.3. First-Stage Adjustment. The824 areas designated for oursamples were selected from2,025 such areas of the UnitedStates. Some sample areasrepresent only themselves andare referred to as self-representing.The remaining areasrepresent other areas similarin selected characteristics andare thus designated non-selfrepresenting.The first-stagefactor reduces the component ofvariation arising from samplingthe non-self-representing areas.4. Second-Stage Adjustment. Thisadjustment brings the estimatesof the total population intoagreement with census-basedestimates of the civilian noninstitutionalizedand nonbarrackmilitary populations for eachstate.B. Sportspersons SampleEvery interviewed person in thesportspersons detailed samplereceived a weight that was theproduct of the following factors:1. Screening Weight. This is theperson’s final weight from thescreening sample.2. Sportspersons Stratum Adjustment.This factor inflates theweights of persons selected forthe detailed sample to accountfor the subsampling done withineach sportsperson stratum.3. Sportspersons NoninterviewAdjustment. This factor adjuststhe weights of the interviewedsportspersons to account forsportspersons selected for thedetailed sample for whomno interview was obtained. Aperson was considered a noninterviewif he or she was notinterviewed in the third wave ofinterviewing.4. Sportspersons Ratio AdjustmentFactor. This is a ratio adjustmentof the detailed sample tothe screening sample withinthe sportspersons samplingstratum. This adjustment bringsthe population estimates ofpersons aged 16 years old andolder from the detailed sampleinto agreement with the sameestimates from the screeningsample, which was a muchlarger sample.C. Wildlife-Watchers SampleEvery interviewed person in thewildlife-watchers detailed samplereceived a weight that was theproduct of the following factors:1. Screening Weight. This is theperson’s final weight from thescreening sample.2. Wildlife-Watchers StratumAdjustment. This factor inflatesthe weights of persons selectedfor the detailed sample toaccount for the subsamplingdone within each wildlifewatcher stratum.3. Wildlife-Watchers NoninterviewAdjustment. This factor adjuststhe weights of the interviewedwildlife-watching participantsto account for wildlife watchersselected for the detailed samplefor which no interview wasobtained. A person was considereda noninterview if he or shewas not interviewed in the thirdwave of interviewing.4. Wildlife-Watchers Ratio AdjustmentFactor. This is a ratioadjustment of the detailedsample to the screening samplewithin wildlife-watcherssampling strata. This adjustmentbrings the population estimatesof persons aged 16 years oldand older from the detailedsample into agreement withthe same estimates from thescreening sample, which was amuch larger sample.ACCURACY OF THE ESTIMATESA sample survey estimate has two typesof error: sampling and nonsampling.The accuracy of an estimate dependson both types of error. The nature ofthe sampling error is known given thesurvey design; the full extent of thenonsampling error is unknown.NONSAMPLING ERRORFor a given estimator, the differencebetween the estimate that would resultif the sample were to include the entirepopulation and the true populationvalue being estimated is known asnonsampling error. There are severalsources of nonsampling error thatmay occur during the development orexecution of the survey. It can occurbecause of circumstances created by theinterviewer, the respondent, the surveyinstrument, or the way the data arecollected and processed. For example,errors could occur because:• The interviewer records the wronganswer, the respondent providesincorrect information, the respondentestimates the requestedinformation, or an unclear surveyquestion is misunderstood by therespondent (measurement error).• Some individuals who should havebeen included in the survey framewere missed (coverage error).122 2011 National Survey of Fishing, Hunting, and Wildlife-Associated Recreation U.S. Fish and Wildlife Service and U.S. Census Bureau