1、Designation: D5791 95 (Reapproved 2017)Standard Guide forUsing Probability Sampling Methods in Studies of Indoor AirQuality in Buildings1This standard is issued under the fixed designation D5791; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers criteria for determining when prob-ability sampling methods should be used
3、to select locations forplacement of environmental monitoring equipment in a build-ing or to select a sample of building occupants for question-naire administration for a study of indoor air quality. Some ofthe basic probability sampling methods that are applicable forthese types of studies are intro
4、duced.1.2 Probability sampling refers to statistical sampling meth-ods that select units for observation with known probabilities(including probabilities equal to one for a census) so thatstatistically defensible inferences are supported from thesample to the entire population of units that had a po
5、sitiveprobability of being selected into the sample.1.3 This guide describes those situations in which probabil-ity sampling methods are needed for a scientific study of theindoor air quality in a building. For those situations for whichprobability sampling methods are recommended, guidance isprovid
6、ed on how to implement probability sampling methods,including obstacles that may arise. Examples of their applica-tion are provided for selected situations. Because some indoorair quality investigations may require application of complex,multistage, survey sampling procedures and because this stan-d
7、ard is a guide rather than a practice, the references inAppendix X1 are recommended for guidance on appropriateprobability sampling methods, rather than including exposi-tions of such methods in this guide.1.4 UnitsThe values stated in SI units are to be regardedas standard. No other units of measur
8、ement are included in thisstandard.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trad
9、e Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1356 Terminology Relating to Sampling and Analysis ofAtmospheres3. Terminology3.1 DefinitionsFor definitions of terms used in this guide,refer to Terminology D1356.3.2 Definitions of Terms Specific
10、to This Standard:3.2.1 census, nsurvey of all elements of the target popu-lation.3.2.2 cluster sample, na sample in which the samplingframe is partitioned into disjoint subsets called clusters and asample of the clusters is selected.3.2.2.1 DiscussionData may be collected for all units ineach sample
11、 cluster or, when a multistage sample is beingselected, the units within the sampled clusters may be furthersubsampled.3.2.3 compositing samples, vphysically combining thematerial collected in two or more environmental samples.3.2.4 expected value, nthe average value of a samplestatistic over all po
12、ssible samples that could be selected usinga specified sample selection procedure.3.2.5 multistage sample, na sample selected in stages suchthat larger units are selected at the first stage, and smaller unitsare selected at each subsequent stage from within the unitsselected at the previous stage of
13、 sampling.3.2.5.1 DiscussionFor assessing the indoor air quality in apopulation of office buildings, individual buildings might beselected at the first stage of sampling, floors selected withinsample buildings at the second stage, and monitoring locations(for example, rooms or grid points) selected
14、on sampled floorsat the third stage.3.2.6 population parameter, na characteristic based on orcalculated from all units in the target population.1This guide is under the jurisdiction of ASTM Committee D22 on AirQuality and is the direct responsibility of Subcommittee D22.05 on Indoor Air.Current edit
15、ion approved Oct. 1, 2017. Published October 2017. Originallyapproved in 1995. Last previous edition approved in 2012 as D5791 95 (2012)1.DOI: 10.1520/D5791-95R17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book
16、 of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recogniz
17、ed principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13.2.6.1 DiscussionThe purpose of selecting a sample isusually to es
18、timate population parameters. Population param-eters cannot actually be calculated unless data are available forall units in the population.3.2.7 probability sample, na sample for which every uniton the sampling frame has a known, positive probability ofbeing selected into the sample.3.2.7.1 Discuss
19、ionThe terms probability sampling andrandom sampling are sometimes used interchangeably.3.2.8 sampling frame, na list from which a sample isselected.3.2.8.1 DiscussionAn ideal sampling frame contains eachmember of the target population exactly once and contains nounits that are not members of the ta
20、rget population. In practice,the sampling frame may miss some members of the targetpopulation (for example, new employees in a building) andinclude some individuals who are not members of the targetpopulation (for example, individuals who no longer work in thebuilding). However, no member of the pop
21、ulation should belisted more than once on the sampling frame.3.2.9 simple random sample, na sample of n elementsselected from the sampling frame in such a way that allpossible samples of n elements have the same chance of beingselected.3.2.10 statistic, na sample-based estimate of a populationparame
22、ter.3.2.11 stratified sample, na sample in which the samplingframe is partitioned into disjoint subsets called strata, andsample units are selected independently from each stratum,possibly at different sampling rates.3.2.12 systematic sample, na sample selected by choosingone of the first k elements
23、 on the sampling frame at random andthen including every k th element thereafter.3.2.13 target population, nthe set of units or elements (forexample, people or locations in space and time) about which asample is designed to provide inferences.3.2.13.1 DiscussionThe target population is sometimesrefe
24、rred to as the population or universe of interest.3.2.14 unbiased estimator, na statistic whose expectedvalue is equal to the population parameter that it is intended toestimate.4. Summary of Guide4.1 When the objectives of an investigation of indoor airquality include extending inferences from a sa
25、mple of units tothe larger population from which those units were selected,probability sampling methods must be used to select thesample units to be observed and measured. Examples include:4.1.1 Estimating the distributions of health and comfortsymptoms experienced by the employees in a particular b
26、uild-ing during a specific week.4.1.2 Estimating the distribution of hourly average concen-trations of specific substances in the breathing zone air in aparticular building during the working hours of a specificweek.4.1.3 Estimating the relationship between measures of en-vironmental conditions in a
27、 building and the health or comfortsymptoms experienced by the occupants.4.1.4 Thus, the study objectives are always a key consider-ation for determining if probability sampling methods arenecessary. Potential objectives for indoor air studies that wouldrequire probability sampling methods are discu
28、ssed explicitlyin Section 6.4.2 Guidance is provided regarding the appropriate prob-ability sampling methods to address these and other goals thatrequire extending inferences from a sample to a specificpopulation. Those sampling methods require construction of asampling frame from which population e
29、lements can beselected. Examples include:4.2.1 A list of all offices or work stations in a building,4.2.2 A grid of potential monitoring locations that effec-tively covers the entire population of interest, and4.2.3 A list of all persons who work in a specific building.4.3 Since environmental concen
30、trations usually vary con-tinuously in time, spatial frame units like those listed in 4.2often must be crossed with temporal units, such as seasons,weeks, days, or hours, to form sampling frame units (forexample, building-seasons, office-weeks, or person-days). Spe-cific issues that must be consider
31、ed when constructing thesetypes of sampling frames are discussed in Section 7.4.4 In addition to constructing sampling frames, a random-ization procedure is necessary so that units can be selectedfrom the frame with known probabilities. Some basic consid-erations for and methods of selecting probabi
32、lity samples forstudies of indoor air quality are presented in Section 8.4.5 Finally, Section 9 discusses considerations for statisticalanalysis and reporting that are peculiar to data collected usingprobability sampling designs. Special statistical analysis meth-ods are necessary when the sampling
33、design includesstratification, clustering, multistage sampling, or unequal prob-abilities of selection.5. Significance and Use5.1 Studies of indoor air problems are often iterative innature. A thorough engineering evaluation of a building (1-4)3is sometimes sufficient to identify likely causes of in
34、door airproblems. When these investigations and subsequent remedialmeasures are not sufficient to solve a problem, more intensiveinvestigations may be necessary.5.2 This guide provides the basis for determining whenprobability sampling methods are needed to achieve statisti-cally defensible inferenc
35、es regarding the goals of a study ofindoor air quality. The need for probability sampling methodsin a study of indoor air quality depends on the specificobjectives of the study. Such methods may be needed to selecta sample of people to be asked questions, examined medically,or monitored for personal
36、 exposures. They may also be neededto select a sample of locations in space and time to bemonitored for environmental contaminants.3The boldface numbers in parentheses refer to the list of references at the end ofthis standard.D5791 95 (2017)25.3 This guide identifies several potential obstacles top
37、roper implementation of probability sampling methods instudies of indoor air quality in buildings and presents proce-dures that overcome those obstacles or at least minimize theirimpact.5.4 Although this guide specifically addresses samplingpeople or locations across time within a building, it alsop
38、rovides important guidance for studying populations of build-ings. The guidance in this document is fully applicable tosampling locations to determine environmental quality orsampling people to determine environmental effects withineach building in the sample selected from a larger populationof buil
39、dings.6. Study Objectives That Require Probability SamplingMethods6.1 Inferences beyond the units actually observed in asample are not rigorously defensible unless the units observedare a probability sample selected from the population to whichinferences will be extended. Thus, probability sampling
40、meth-ods are needed whenever inferences will be extended from theunits observed in a sample to a larger population. The need forsuch inferences depends directly on the objectives of the study.The study objectives may include characterizing a buildingsoccupants using a survey, or characterizing a bui
41、ldings airquality using environmental monitoring, or a combination ofboth.6.2 Occupant Survey:6.2.1 A sample of building occupants may be asked tocomplete a questionnaire or to submit to a physical examina-tion. If the intention is to make inferences from the sampleregarding the health and comfort s
42、ymptoms of all the employ-ees of the building, a census of all building occupants or aprobability sample selected from them is required. The occu-pants would typically be asked about their health and comfortsymptoms for a specific period of time (for example, the daythat the survey is administered,
43、the previous week, month, oryear, and so forth). Developing a valid and reliable question-naire is a complex process and is not directly addressed by thisguide (5).6.2.2 Specific study objectives that require inferences to apopulation of building occupants include the following:6.2.2.1 Estimate the
44、distribution of health and comfortsymptoms in a building either before beginning air qualitymeasurements, after implementing remedial measures, or as ameasure of the magnitude of a potential indoor air problem.6.2.2.2 Estimate the distribution of health and comfortsymptoms in a building with reporte
45、d problems and in anotherbuilding studied for comparison purposes.6.2.2.3 Estimate the relationship of health and comfortsymptoms with worker characteristics, such as age, sex, worklocation, or type of work performed.6.2.3 When inferences regarding the occupants of a buildingare needed, a census of
46、all the building occupants may benecessary. For example, a census of building occupants may beneeded to establish statistical differences in occupant comfortor health symptoms between different work areas (for example,floors) within a building. In other cases (for example, estimat-ing the relative f
47、requency of complaints in a building with alarge number of workers), a probability sample may providesufficient precision at less cost.6.2.4 If the characteristics measured in a questionnaire aretemporally dependent (for example, comfort and health symp-toms on the day of questionnaire administratio
48、n), a sample ofpeople and time periods may be needed (for example, a sampleof person-days within a given week). Moreover, the surveymay need to be replicated across time (that is, repeated indifferent seasons).6.2.5 A successful occupant survey requires that a largeportion of the sample subjects com
49、plete the survey. Forexample, the United States Office of Management and Budgetusually requires 75 % or more for federally funded surveys.Thus, the success of a survey may depend upon the burden itimposes, pre-survey publicity (for example, newsletters orunion endorsements), and follow-up of nonrespondents. Thesurvey should be conducted in such a manner that people aresufficiently motivated to participate but not unduly alarmedabout a potential air quality problem. Finally, residual nonre-sponse is inevitable, and survey data analysis procedures thatutilize
