WordNet

be a student; follow a course of study; be enrolled at an institute of learning
a room used for reading and writing and studying; "he knocked lightly on the closed door of the study"
applying the mind to learning and understanding a subject (especially by reading); "mastering a second language requires a lot of work"; "no schools offer graduate study in interior design" (同)work
a composition intended to develop one aspect of the performers technique; "a study in spiccato bowing"
a state of deep mental absorption; "she is in a deep study"
someone who memorizes quickly and easily (as the lines for a part in a play); "he is a quick study"
give careful consideration to; "consider the possibility of moving" (同)consider
learn by reading books; "He is studying geology in his room"; "I have an exam next week; I must hit the books now" (同)hit the books
think intently and at length, as for spiritual purposes; "He is meditating in his study" (同)meditate, contemplate
provide with or construct with studs; "stud the wall"
ornament consisting of a circular rounded protuberance (as on a vault or shield or belt) (同)rivet
poker in which each player receives hole cards and the remainder are dealt face up; bets are placed after each card is dealt (同)stud poker
adult male horse kept for breeding (同)studhorse
a man who is virile and sexually active (同)he-man, macho-man
the act of observing; taking a patient look (同)observance, watching
the act of making and recording a measurement
a remark expressing careful consideration (同)reflection, reflexion
facts learned by observing; "he reported his observations to the mayor"

PrepTutorEJDIC

〈U〉(一般に)『勉強』,学習すること / 〈C〉(…の)勉強,研究《+of+名》 / 〈C〉〈U〉(…の)『綿密な調査』,検討《+of+名》 / 〈C〉研究対象(問題,事項);学科 / 〈C〉『書斎』,勉強部屋 / 〈C〉(美術・文学などの)習作,試作,スケッチ,(音楽の)練習曲,エチュード / …‘を'『勉強する』,学ぶ,研究する / …‘を'『よく注意して見る』,しげしげと見る / …‘を'『調査する』,検討する / …‘を'考慮する,配慮する / 〈せりふなど〉‘を'覚えようとする / 『勉強する』,学ぶ,研究する
《おもに米》種馬 / 《集合的に》(一群の)繁殖用動物(種馬,種牛など)
(インテリアなどに用いる)飾りびょう / カフスボタン,カラーボタン / (建物の)間柱 / (…を)…‘に'ちりばめる《+名+with+名》 / …‘に'点在(散在)している / …‘に'間柱をつける
〈U〉〈C〉(…を)『観察』(『注意』)『すること』;(…の)(特に,科学的)観察《+『of』+『名』》 / 〈U〉『観察力』,注意力 / 《複数形で》(…について)観察されたもの,(…の)観察記録《+『of』(『on』)+『名』》 / 〈C〉(観察に基づく)発言,意見《『observation on』(『about』)+『名』…についての意見》
観察の,観察上の

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/04/09 16:08:13」(JST)

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In epidemiology and statistics, an observational study draws inferences about the possible effect of a treatment on subjects, where the assignment of subjects into a treated group versus a control group is outside the control of the investigator.^[1]^[2] This is in contrast with experiments, such as randomized controlled trials, where each subject is randomly assigned to a treated group or a control group. The assignment of treatments may be beyond the control of the investigator for a variety of reasons:

A randomized experiment would violate ethical standards. Suppose one wanted to investigate the abortion – breast cancer hypothesis, which postulates a causal link between induced abortion and the incidence of breast cancer. In a hypothetical controlled experiment, one would start with a large subject pool of pregnant women and divide them randomly into a treatment group (receiving induced abortions) and a control group (bearing children), and then conduct regular cancer screenings for women from both groups. Needless to say, such an experiment would run counter to common ethical principles. (It would also suffer from various confounds and sources of bias, e.g., it would be impossible to conduct it as a blind experiment.) The published studies investigating the abortion–breast cancer hypothesis generally start with a group of women who already have received abortions. Membership in this "treated" group is not controlled by the investigator: the group is formed after the "treatment" has been assigned.^{[citation needed]}

The investigator may simply lack the requisite influence. Suppose a scientist wants to study the public health effects of a community-wide ban on smoking in public indoor areas. In a controlled experiment, the investigator would randomly pick a set of communities to be in the treatment group. However, it is typically up to each community and/or its legislature to enact a smoking ban. The investigator can be expected to lack the political power to cause precisely those communities in the randomly selected treatment group to pass a smoking ban. In an observational study, the investigator would typically start with a treatment group consisting of those communities where a smoking ban is already in effect.^{[citation needed]}

A randomized experiment may be impractical. Suppose a researcher wants to study the suspected link between a certain medication and a very rare group of symptoms arising as a side effect. Setting aside any ethical considerations, a randomized experiment would be impractical because of the rarity of the effect. There may not be a subject pool large enough for the symptoms to be observed in at least one treated subject. An observational study would typically start with a group of symptomatic subjects and work backwards to find those who were given the medication and later developed the symptoms. Thus a subset of the treated group was determined based on the presence of symptoms, instead of by random assignment.^{[citation needed]}

Degree of usefulness and reliability

Although observational studies cannot be used as reliable sources to make statements of fact about the "safety, efficacy, or effectiveness" of a practice,^[3] they can still be of use for some other things:

"[T]hey can: 1) provide information on “real world” use and practice; 2) detect signals about the benefits and risks of...[the] use [of practices] in the general population; 3) help formulate hypotheses to be tested in subsequent experiments; 4) provide part of the community-level data needed to design more informative pragmatic clinical trials; and 5) inform clinical practice."^[3]

Discussion

In all of those cases, if a randomized experiment cannot be carried out, the alternative line of investigation suffers from the problem that the decision of which subjects receive the treatment is not entirely random and thus is a potential source of bias. A major challenge in conducting observational studies is to draw inferences that are acceptably free from influences by overt biases, as well as to assess the influence of potential hidden biases.

An observer of an uncontrolled experiment (or process) records potential factors and the data output: the goal is to determine the effects of the factors. Sometimes the recorded factors may not be directly causing the differences in the output. There may be more important factors which were not recorded but are, in fact, causal. Also, recorded or unrecorded factors may be correlated which may yield incorrect conclusions. Finally, as the number of recorded factors increases, the likelihood increases that at least one of the recorded factors will be highly correlated with the data output simply by chance.

In lieu of experimental control, multivariate statistical techniques allow the approximation of experimental control with statistical control, which accounts for the influences of observed factors that might influence a cause-and-effect relationship. In medicine and the social sciences, investigators may use matching to compare units that nonrandomly received the treatment and control. One common approach is to use propensity score matching in order to reduce confounding.^[4]

In 2007, several prominent medical researchers issued the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement, in which they called for observational studies to conform to 22 criteria that would make their conclusions easier to understand and generalise.^[5]

References

^ "Observational study". Retrieved 2008-06-25.
^ Porta M (editor). A dictionary of epidemiology. 5th. edition. New York: Oxford University Press, 2008.
^ ^a ^b "Although observational studies cannot provide definitive evidence of safety, efficacy, or effectiveness, they can: 1) provide information on “real world” use and practice; 2) detect signals about the benefits and risks of complementary therapies use in the general population; 3) help formulate hypotheses to be tested in subsequent experiments; 4) provide part of the community-level data needed to design more informative pragmatic clinical trials; and 5) inform clinical practice." "Observational Studies and Secondary Data Analyses To Assess Outcomes in Complementary and Integrative Health Care." Richard Nahin, Ph.D., M.P.H., Senior Advisor for Scientific Coordination and Outreach, National Center for Complementary and Alternative Medicine, June 25, 2012
^ Rosenbaum, Paul R. 2009. Design of Observational Studies. New York: Springer.
^ von Elm E, Altman DG, Egger M, Pocock SJ, Gøtzsche PC, Vandenbroucke JP (2007). [www.strobe-statement.org "The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) Statement: Guidelines for Reporting Observational Studies"]. PLoS Med. 4 (10): e296. doi:10.1371/journal.pmed.0040296. PMC 2020495. PMID 17941714.

Bibliography

Paul R. Rosenbaum (2002). Observational Studies, 2nd edn. New York: Springer-Verlag.
"NIST/SEMATECH Handbook on Engineering Statistics" at NIST

UpToDate Contents

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English Journal

Restraint use and seating position among child car passengers: An observational study in Shanghai.

Pan S, Du W, Jiang F, Bilston L, Brown J, Shen X.SourceEmergency Department, Xinhua Hospital, and Faculty of Medicine, Shanghai Jiaotong University, China; Shanghai Paediatric Research Institute, Shanghai Key Laboratory of Children's Environmental Health, China.
Accident; analysis and prevention.Accid Anal Prev.2011 Nov;43(6):2195-9. Epub 2011 Jul 22.
Child passenger restraint practices in China are poorly characterized and few direct observational studies have been performed. This study aims to describe child passenger restraint use and to investigate factors influencing the restraint practices. A cross-sectional observational study was conducte
PMID 21819852

Japanese Journal

Evaluation of an Assessment System for the JRS 2005: A-DROP for the Management of CAP in Adults

Kohno Shigeru,Seki Masafumi,Watanabe Akira,the CAP Study Group
Internal Medicine 50(11), 1183-1191, 2011-06-01
… The goal of the present study was to evaluate the utility of the A-DROP criteria for these described purposes. … Methods An observational survey was conducted between July 2006 and March 2007, and patients with CAP were prospectively surveyed using consecutive enrollment methods. …
NAID 120003238504