Kvalitetsbegrepp och riktlinjer för kvalitets - Statistiska centralbyrån

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32 Quality and statistics The term "statistics" is used with somewhat different meanings. Here its chief interpretation is "a summarising numerical description of the conditions for a group". Statistics are produced to provide information which sheds light on subject matter problems. They often constitute vital basic information in planning and decision contexts. They also provide information to the general public, investigators, researchers and others about "the state of affairs". The basic notion in statistics contexts is statistical characteristic, which is a numerical value determined as follows. A statistical measure (e.g. "number of", mean or median) is used to summarise individual variable values for the objects in a group. The totality of considered objects is called the population. Examples of statistical characteristics are : (i) Production value for the Swedish shipbuilding industry during 1998. In this case the population = Swedish shipbuilding enterprises (during 1998), the variable = production value during 1998, the statistical measure = sum. (ii) Average disposable income during 1998 for a Stockholm family with two children. In this case the population = families with two children who 1998 lived in Stockholm, the variable = disposable income, the statistical measure = mean. The purpose of a statistical survey is to acquire information about the value of one or more statistical characteristics for a population, usually also for various subgroups of the population. The characteristics with which the survey is concerned are called the target characteristics. They have "true" but unknown values. A survey typically comprises two main steps, first the collection of primary data for individual objects and thereafter the compilation of statistics, which estimate the target characteristics. The word "estimate" used above indicates that statistics usually do not provide perfectly true values of target characteristic, but are subject to some uncertainty. The "categorical imperative" for a surveyor is to strive for estimates which are unbiased ("on average correct"). There are many potential sources of inaccuracy. For a sample survey the obvious source of inaccuracy is that perfect information about a population cannot be gained by observing only a sample of its members. Total inspection surveys as well as sample surveys are affected also by other kinds of disturbances, which contribute to the inaccuracy of the final statistics. Sources of inaccuracy, in addition to sampling, which are discussed in more detail later on are: frame deficiencies, measurement errors, non - response, processing errors and non - perfect model assumptions. When the "total quality" concept formulated in the previous section is applied to the "product" statistics it leads to the following definition. (iii) Quality of statistics refers to all aspects of statistics, which are relevant for how well they meet users' needs for statistical information. As a background to the quality concept to be formulated below we will comment on some aspects of statistics, which are important to a majority of users. The subsequent section "Elaboration on the quality components" contains a more detailed discussion of the aspects. Mostly users have a strong desire for timely statistics, meaning (at least ideally) that they describe the "now" state of affairs. Factors which affect timeliness are swiftness in data collection and subsequent compilations, and for repeated surveys how frequently they are executed. A common and important usage of statistics is for comparisons, over time (via time series) as well as between groups. Fair comparisons require coherence of the target
characteristics to be compared. This requirements is also important when statistics from different sources are to be combined. Statistics are made available to users by different dissemination forms, via different media (e.g. on paper, on diskettes and other electronic media) and through different channels (e.g. periodical reports by mail, year books, Reuter, Internet). Statistical information is presented in different ways, in tables, charts, text, etc. Some users want statistics other than those published regularly. Sometimes such statistics, although not published, are available by the producer, in other cases they can be created by special processing of the primary data. A further alternative, which is requested by many users, in particular researchers and investigators, is direct access to (de-identified) primary data, which allows the users to derive statistics and make analyses themselves according to their own specific interests. Users' confidence in statistics depends on their beliefs about errors, unintentional as well as intentional. Not even a very careful statistics producer can avoid some unintentional uncertainty in the statistics. It is a fact of life, however, that deliberately false, non-objective, statistics sometimes occur, which of course is a serious quality deficiency. However, the aspect objectivity is not included in the quality concept. It is more or less impossible to judge if statistics are objective or not, and producers of false statistics would not inform their users about it. As regards Sweden, the law 1992 : 889 states the following. "Official statistics shall be objective and generally available". As already said, "user" refers to existing as well as potential users. There will always be organisations and persons who consider that their needs are not met by the official statistics, either because the statistics are not produced at all or because available statistics is not accurate enough. Producers should be keen to take such requirements into account when evaluating and revising surveys. Quality concept for official statistics How a user delimits the portion of statistics, with which his/her quality opinion is concerned, depends on his/her specific subject matter problem and application interest. "The statistics" may consist of a single value, of all statistics from a particular survey or statistics from different surveys to be used together. It may also concern "flows" (over time) of statistics. It is of course so that the more the concerned portion of statistics encompasses, the more quality aspects does it have. The following quality concept is meant to be applicable whatever the statistics extent may be, but for small "statistics packages" some of the quality components may be irrelevant. There is no self-evident division of the total collection of quality aspects for statistics into main aspects and sub-aspects. The quality concept which is presented below has the following five main components. (1) Contents, which concerns the target characteristics. (2) Accuracy, concerning sources of inaccuracy and their effects on the statistics. (3) Timeliness, concerning time aspects of relevance for how well the statistics describe the "now" situation. (4) Coherence especially comparability, concerning possibilities to make comparisons, over time and between groups, and to use the statistics jointly with statistics from other sources. (5) Availability and clarity, concerning physical availability of the statistics and their understandability. It has been emphasised earlier that the quality concept is user oriented. As a consequence, it should as far as possible be formulated from the users' point of view (not the producers'). There are exceptions from this principle, however, particularly for the quality component "accuracy". For the user "overall accuracy" is of chief interest, while its decomposition into different uncertainty sources, as is made in the quality is of a technical, producer oriented nature. The reason for specifying "nar- 33
Page 1 and 2: (Huvud) Kvalitetsbegrepp och riktli
Page 3 and 4: Förord Frågor som har att göra m
Page 5 and 6: Bakgrund för och syfte med detta M
Page 7 and 8: Kvalitetsbegrepp för officiell sta
Page 9 and 10: Meddelanden per post, årsbok, på
Page 11 and 12: Kvalitetskomponenternas innebörd I
Page 13 and 14: 1.2 Fullständighet Denna kvalitets
Page 15 and 16: osäkerhetens konsekvenser, befinne
Page 17 and 18: Användares jämförelsemöjlighete
Page 19 and 20: Riktlinjer för kvalitetsdeklaratio
Page 21 and 22: Idealt anges statistikvärdens osä
Page 23: Ange annan statistik som är särsk
Page 26 and 27: 20 beräkningsregel för sammanfatt
Page 28 and 29: 22 att bestämma precis vilka obser
Page 30 and 31: 24 lens celler är dock fortfarande
Page 32 and 33: 26 tekniskt uttryckt ha så liten (
Page 35: Bilaga 2. Summarisk redovisning av
Page 40 and 41: 34 row" uncertainty sources is that
Page 42 and 43: 36 Examples of study domains : Two
Page 44 and 45: 38 2.2 Sources of inaccuracy At lea
Page 46 and 47: 40 Survey frequency matters not onl
Page 48 and 49: 42 AVAILABILITY and CLARITY Concern
Page 51 and 52: Kvalitetsdeklaration av Årlig befo
Page 53 and 54: "kvot", "intensitet" och "risk" som
Page 55 and 56: Kommentar angående regionala indel
Page 57 and 58: myndigheters massutsändning av bre
Page 59 and 60: Medborgarskapsbyten Fr.o.m. 1974 s
Page 61 and 62: Kvalitetsdeklaration av Arbetskraft
Page 63 and 64: Latent arbetssökande En delgrupp a
Page 65 and 66: precist beskriva vilka korsindelnin
Page 67 and 68: medförde avsevärd reduktion av ti
Page 69 and 70: Blankett för ny klassificering Bla
Page 71 and 72: 2.2.5 Bearbetning Granskning och r
Page 73 and 74: Tusental Tusentals 1420 1400 1380 1
Page 75: Henkel M (1994):. Dokumentförteckn
Page 78 and 79: 72 1.1.1 Objekt och population Obje
Page 80 and 81: 74 Antalet insamlade prisuppgifter
Page 82 and 83: 76 för denna ”vara” genom att
Page 84 and 85: 78 Kvalitetsdeklaration av Gödselm
Page 86 and 87: 80 2.2.2 Ramtäckning LBR, som anv
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82 från producerad mängd stallgö
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Kvalitetsbegrepp och riktlinjer för kvalitets - Statistiska centralbyrån

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