首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 390 毫秒
1.
Publication bias can occur when a study is not published in an academic journal because the study did not find a statistically significant result. It can bias meta-analytic estimates upwards because the meta-analyses are missing studies that provide small estimates of the effect size under study. This paper describes the trim and fill technique of estimating the impact of publication bias on meta-analyses (Duval & Tweedie, 2000a, 2000b) and provides a working example. A sample of 68 meta-analyses of communication research were tested for publication bias using the trim and fill technique. The results suggest that most communication meta-analyses are not substantially affected by publication bias.  相似文献   

2.
An argument is advanced for the propositions that a lack of statistically significant findings does not automatically justify rejecting a scientific article for publication or mean that the findings are necessarily uninformative. Systematically declining publication for nonsignificant results leads to negative consequences that include distorting scientific literatures, making hypotheses and theories less falsifiable, depriving meta-analyses of an accurate sample of prior findings, and encouraging questionable research practices. Providing effect sizes and confidence intervals can make findings more informative, regardless of whether the finding is p < .05.  相似文献   

3.
This paper presents the first meta-analysis of studies that computed correlations between the h index and variants of the h index (such as the g index; in total 37 different variants) that have been proposed and discussed in the literature. A high correlation between the h index and its variants would indicate that the h index variants hardly provide added information to the h index. This meta-analysis included 135 correlation coefficients from 32 studies. The studies were based on a total sample size of N = 9005; on average, each study had a sample size of n = 257. The results of a three-level cross-classified mixed-effects meta-analysis show a high correlation between the h index and its variants: Depending on the model, the mean correlation coefficient varies between .8 and .9. This means that there is redundancy between most of the h index variants and the h index. There is a statistically significant study-to-study variation of the correlation coefficients in the information they yield. The lowest correlation coefficients with the h index are found for the h index variants MII and m index. Hence, these h index variants make a non-redundant contribution to the h index.  相似文献   

4.
This study uses meta-analysis to compare the persuasive effects of metaphorical and literal messages and assess various theoretical explanations for the relatively greater persuasiveness of metaphor. The meta-analysis includes studies from 2001 to 2015 that use various message formats and topics. Results indicate an overall effect size of r = 0.09, p < .001, 95% CI [0.06, 0.12], which supports the conclusion that metaphorical messages are more persuasive than literal messages. Moderator analyses indicate differences in effect sizes based on metaphor target familiarity, message topic, and message format. A meta-regression using the theoretical moderators indicates that message format was the strongest predictor of variation in effect size. This study provides implications related to the theoretical mechanism behind the greater persuasive effects of metaphor.  相似文献   

5.
This study of 601 3rd-6th grade boys and girls examined implicit and explicit attitudes of anti-fat bias along with media exposure variables and appearance anxiety. In this study, predictors of implicit attitudes of bias were measured and then those same implicit measures were tested as possible predictors of more explicit measures of anti-fat bias. Given the uniqueness of the measures with a sample of this age and the self-report measures of media use, the hope was that the results may prove helpful in understanding the complicated factors related to children's attitudes and beliefs about weight bias in order further explain how and why thinness is regarded as such an important social and cultural attribute. Findings suggest that exposure to an image of an overweight child and fear of negative appearance evaluations were the strongest predictors of two measures of explicit anti-fat bias. Furthermore, implicit attitudes representative of fat bias were also evident across the sample. Greater television exposure was related to decreased levels of anti-fat bias and more favorable assessments of overweight subjects viewed in photographs; thus, findings suggest several factors are important in better understanding the correlates related to anti-fat bias in children.  相似文献   

6.
Although a growing number of studies are examining the relationship between Internet use and political participation, varying study characteristics make the overall effect size difficult to estimate. Using a meta-analysis, we estimated the mean effect size and tested whether the effect size was influenced by study characteristics. Data for this meta-analysis were derived from 56 papers reporting 63 independent studies. Results revealed that Internet use had a weak relationship with political participation (rc?=?.22). Moderator analyses demonstrated that type of Internet use, Internet use measure, Internet use for news, type of political participation, sample origin, and survey year significantly moderated the relationship between Internet use and political participation. For instance, Internet use including news (rc?=?.27) had a significantly stronger relationship with political participation than did Internet use excluding news (rc?=?.19). European samples (rc?=?.27) had the largest mean correlation followed by North American samples (rc?=?.23) and Asian samples (rc?=?.18) in decreasing order of strength of relationship. The theoretical and methodological implications of the findings are discussed.  相似文献   

7.
《资料收集管理》2013,38(1-2):71-88
This study examines the relationship between the reviewing media and classical music recording collections in libraries in order to determine if reviews are an important selection tool for these collections. As previous studies have shown that there is a correlation between the number of reviews a work receives and the number of libraries owning that work, it is hypothesized that this relationship holds true for classical music recordings. A second hypothesis is that a correlation exists between the nature of the reviews, positive or negative, a recording receives and its ownership by libraries. The number and direction of a random sample of two hundred classical recordings released in 1989 is tallied from the review index in MLA Notes, as is the number of OCLC libraries owning each item. These data suggest that there is no correlation between the number of reviews a work receives and the number of libraries owning that work, nor between the number of positive reviews a work receives and its ownership by libraries. Possible reasons for these findings are discussed, and further questions are raised.  相似文献   

8.
《Communication monographs》2012,79(4):388-396

In a useful article regarding testing for moderator variables in meta‐analysis, Hall and Rosenthal (1991) suggest, among other things, that when the sample of studies is large enough, it is acceptable to use ordinary inferential statistics such as the analysis of variance to test for moderator variables. However, because meta‐analytic data points (effect sizes) differ in important ways from those for which ordinary inferential statistics were designed, we recommend that analysts use conventional meta‐analytic statistics, which are at least potentially more informative about the literature in question. Hall and Rosenthal also suggest that tests of effect size variability should play a minimal role in meta‐analytic model tests. We concur that these tests of homogeneity cannot alone test for moderator variables and that at least tests between mean effect sizes should be performed. However, consistent with Hedges and Olkin's (1985) meta‐analytic framework, we show how homogeneity tests provide additional and valuable information regarding how completely a moderator (or set of moderators) explains the variation of effect sizes. Therefore, these goodness‐of‐fit statistics may prove quite valuable, especially in meta‐analyses of highly variable study outcomes. We further recommend that in meta‐analyses for which study outcomes are already consistent, analysts should continue to perform model tests if they have theoretical expectations about moderators. We discuss these and other meta‐analytic model testing concerns.  相似文献   

9.
Server selection is an important subproblem in distributed information retrieval (DIR) but has commonly been studied with collections of more or less uniform size and with more or less homogeneous content. In contrast, realistic DIR applications may feature much more varied collections. In particular, personal metasearch—a novel application of DIR which includes all of a user’s online resources—may involve collections which vary in size by several orders of magnitude, and which have highly varied data. We describe a number of algorithms for server selection, and consider their effectiveness when collections vary widely in size and are represented by imperfect samples. We compare the algorithms on a personal metasearch testbed comprising calendar, email, mailing list and web collections, where collection sizes differ by three orders of magnitude. We then explore the effect of collection size variations using four partitionings of the TREC ad hoc data used in many other DIR experiments. Kullback-Leibler divergence, previously considered poorly effective, performs better than expected in this application; other techniques thought to be effective perform poorly and are not appropriate for this problem. A strong correlation with size-based rankings for many techniques may be responsible.  相似文献   

10.
  相似文献   

11.
This paper addresses the problem of estimating the size of a deep web data source that is accessible by queries only. Since most deep web data sources are non-cooperative, a data source size can only be estimated by sending queries and analyzing the returning results. We propose an efficient estimator based on the capture–recapture method. First we derive an equation between the overlapping rate and the percentage of the data examined when random samples are retrieved from a uniform distribution. This equation is conceptually simple and leads to the derivation of an estimator for samples obtained by random queries. Since random queries do not produce random documents, it is well known that the traditional methods by random queries underestimate the size, i.e., those estimators have negative bias. Based on the simple estimator for random samples, we adjust the equation so that it can handle the samples returned by random queries. We conduct both simulation studies and experiments on corpora including Gov2, Reuters, Newsgroups, and Wikipedia. The results show that our method has small bias and standard deviation.  相似文献   

12.
This brief note hopes to dispel some apparent confusions concerning statistical power, especially ones stemming from power computations based on treating an observed sample effect size as the population effect of interest ("post hoc," "observed," or "retrospective" power). Some after-the-fact power analyses can be useful for presentation purposes but only when based on population effect sizes of independent interest. It is recommended that labels such as "post hoc power," "observed power," "retrospective power," and "a priori power" be avoided, that reported power figures be accompanied by specification and justification of the values used to compute power, and that results characteristically be described with effect sizes, confidence intervals, and p values.  相似文献   

13.
Although equivalence testing is preferred when a researcher's goal is to support the null hypothesis (i.e., no substantial effect), equivalence tests are virtually unknown and unused in the communication field. This article provides the rationale for and theoretical background of equivalence testing and offers examples of equivalence tests for the independent and dependent groups t-test and tests of association using Pearson's coefficient or correlation. From a review of meta-analyses, we provide tables of commonly observed effect-sizes across subdisciplines and topic areas in communication and offer these as a guideline for choosing minimum substantial effects (Δ) in equivalence testing when no other information source is available. To facilitate the adoption of equivalence tests in future research, we provide easy-to-use custom dialogs for SPSS which greatly simplify their computation and application.  相似文献   

14.
OBJECTIVE: Clinical decisions based on a meta-analysis that is based on an ineffective retrieval strategy may have serious negative consequences for patients. The study objective was to investigate the extent to which meta-analyses report proof of their retrieval strategies' effectiveness. METHODS: The authors examined a random sample (n = 100) of articles in the 1996 to 2002 full-text subset of Ovid MEDLINE indexed as "meta-analysis." We classified the articles in three ways: the article (A) reported both a retrieval strategy in sufficient detail (such that it could be repeated) and with evidence of the strategy's effectiveness, (B) reported a retrieval strategy in sufficient detail but not with evidence of the strategy's effectiveness, or (C) neither reported a strategy in detail nor evidence of the strategy's effectiveness. Articles classified as (A) were further classified according to the level of evidence reported. RESULTS: Of the eighty-nine articles in our final analysis, six (6.7%) were classified as category (A), fifty-seven (64%) as (B), and twenty-six (29%) as (C). Articles in category (A) reported a previously validated search, a published strategy, or strategy based on expert opinion. CONCLUSION: Peer-review standards must be developed that require authors of meta-analyses to report evidence for the effectiveness of their retrieval strategies.  相似文献   

15.
This investigation tested the notion that speakers should own their emotions by using I-messages rather than You-messages when conveying their feelings. In Study 1, hypothetical self-attributed (I) emotion messages were compared to other-attributed (You) messages, with an I-You message added in Study 2. In both studies, the effect of both positive and negative emotion statements on perceived politeness, effectiveness, and emotional reactions were assessed. No differences were found in reactions to the message forms for negative emotions, but both studies provided evidence for differences in respondents' reaction to positive emotional expressions. These results suggest a self-serving bias; recipients do not distinguish between ways of phrasing negative emotions expressed to them, but apparently appreciate being given credit for speakers' positive emotions. Implications for therapists, communication consultants, and practitioners are discussed.  相似文献   

16.
目的：评价PRISMA声明对发表于《循证医学》杂志的干预类系统评价/Meta分析报告质量的影响。方法：根据纳入排除标准,纳入2001-2011年发表于《循证医学》的干预性试验系统评价/Meta分析,采用PRISMA量表对纳入系统评价/Meta分析进行评价,用Meta Analyst软件进行统计分析。结果：共纳入70个系统评价/Meta分析,涉及14个疾病谱。 PRISMA的发布和高校作者发表的系统评价/Meta分析,可以提高其报告质量（P＜0．05）,基金资助和作者数量对文献报告质量影响不大。结论：发表于《循证医学》杂志的系统评价/Meta分析在文献检索、筛选、偏倚评估和其他分析方法等方面亟待改善,报告质量有待提高。 PRISMA的发布可在整体上改善系统评价/Meta分析的报告质量。  相似文献   

17.
This investigation tested the notion that speakers should own their emotions by using I-messages rather than You-messages when conveying their feelings. In Study 1, hypothetical self-attributed (I) emotion messages were compared to other-attributed (You) messages, with an I-You message added in Study 2. In both studies, the effect of both positive and negative emotion statements on perceived politeness, effectiveness, and emotional reactions were assessed. No differences were found in reactions to the message forms for negative emotions, but both studies provided evidence for differences in respondents' reaction to positive emotional expressions. These results suggest a self-serving bias; recipients do not distinguish between ways of phrasing negative emotions expressed to them, but apparently appreciate being given credit for speakers' positive emotions. Implications for therapists, communication consultants, and practitioners are discussed.  相似文献   

18.
It is a common assumption that in many countries mass mediacensorship is imposed by an authoritarian government on an unwillingpublic. This study examines public opinion about televisioncensorship in the island nation of Singapore. More specifically,we tested the third-person effect hypothesis, which suggeststhat people expect media content to have more negative influenceon others than on themselves, and that some support for censorshipis based on that perceptual bias. Data for the study came from face-to-face interviews with 506randomly selected Singaporeans who evaluated ten categoriesof ‘sensitive’ television content. Results revealed(1) a substantial perceptual bias in all content categories;(2) generally strong opinion favoring censorship of televisioncontent; and (3) a significant relationship between these twofactors, suggesting that people may support censorship of mediain part because of a tendency to overestimate its negative influence.  相似文献   

19.
《Public Library Quarterly》2013,32(3):281-290
A random sample of 100 titles was taken of monographs cataloged by the Indiana Cooperative Library Services Authority (INCOLSA) Processing Center from 1975 through 1978. The cataloging, done using the OCLC system, reflected a 95% find rate in the OCLC data base; the 5% original input remaining is not unusual for public libraries using this system. An investigation of the overlap of the sample with five public library collections showed a positive correlation between target library size and find rate. However, because 75% of the sample was nonfiction (higher than expected for small and medium sized public libraries, which make up the bulk of the processing center users), the processing center collection file may not be typical of the total collections of such libraries. To gain an indication of the value of the processing center file in resource sharing, a furfher study was made of the 18% of the sample not found in any of the five public libraries searched. An additional 7% of the sample was located in Indiana using the OCLC data base; the remaining 11% was not easily located in the state. This is taken as evidence of the importance of small and medium sized public libraries in providing access to specialized or uncommon materials.  相似文献   

20.
Questionable research practices (QRPs) pose a major threat to any scientific discipline. This article analyzes QRPs with a content analysis of more than three decades of published experimental research in four flagship communication journals: Journal of Communication, Communication Research, Journalism & Mass Communication Quarterly, and Media Psychology. Findings reveal indications of small and insufficiently justified sample sizes, a lack of reported effect sizes, an indiscriminate removal of cases and items, an increasing inflation of p-values directly below p < .05, and a rising share of verified (as opposed to falsified) hypotheses. Implications for authors, reviewers, and editors are discussed.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号