The Da Vinci crock

[hi gene]

Bradford Hill has listed nine aspects concerned with the association between exposure and disease which need to be considered. The first of these is the strength of the association. A strongly elevated relative risk is more likely to reflect a causal association than is a slightly or moderately increased risk. Consistency of findings across studies conducted with different methodologies and in different settings, is another aspect. A third characteristic is specificity, that the exposure causes a particular disease, e.g. the observation that cigarette smoking is associated with squamous cell carcinoma of the respiratory tract. An important condition is the Sequence of events: the potentially causative factor must precede the effect, which in this context is disease. The dose-response relationship, or biological gradient, is another aspect. For example, massive exposure to sunlight is more likely to cause melanoma in susceptible individuals than is little or moderate sunlight. Biological plausibility is an aspect which is important, but depends on the biological knowledge of the day. The association should be consistent with what is generally known about the occurrence of the disease, its natural history and pathophysiology, and should not conflict with this knowledge. The causal interpretation of an association is furthered if there is experimental evidence in support of it, for example if elimination of exposure reduces the incidence of the disease. The ninth aspect is analogy. For example, if a virus is shown to be oncogenic in animal studies, we are more prone to accept that the human papilloma virus may be the cause of cervical cancer in humans. In his essay on association and causation, Bradford Hill notes that " none of my nine viewpoints can bring indisputable evidence for or against the cause-and-effect hypothesis and none can be required as a sine qua non ". The challenge of assessing causation is one of many fascinating aspects of epidemiological research.

Assuming you establish causality, how do you go for estimating much of the morbidity and mortality from a disease, for instance, might be prevented by interventions? Just curious, yanno

[Barbara Dente]

Assuming you establish causality, how do you go for estimating much of the morbidity and mortality from a disease, for instance, might be prevented by interventions? Just curious, yanno

Screeing.



Screening test construction involves both traditional and unique psychometry. Nevertheless, screens should adhere to standards for any other educational and psychologist test including evidence of:

- Standardization
- Reliability
- Validity
- Criterion-related reliability

Standardization

This should include a large nationally representative population (rather than a referred population). Ideally, the sample should be a naturalistic one and not a concatenation of groups known to be either normal or abnormal (because this generally eliminates gradations in functioning that characterize children to whom screening tests are applied (e.g., those with below average but not disabled performance).

Reliability

Information should be included on internal consistency, inter-rater reliability, and test-retest reliability. Stability (longer-term test-retest reliability) is sometimes included although given the rapid changes in developmental performance set against a small set of items, stability indicators are not likely to be strong or meaningful.

Validity

Includes concurrent validity (a comparison of screening measures to diagnostic measures). Ideally concurrent validation should involve a test battery that samples the same range of developmental tasks measured by the screening test (e.g., if motor, language and academic skills are measured, the diagnostic battery should include motor, language and academic tasks). Discriminant validity studies are also desirable because they show how well a screening test detects the specific kinds of problems. In the case of broad-band developmental screens, discriminant validity studies should illustrate the extent to which the more common disabling conditions such as language impairment, mental retardation, learning disabilities, autism and cerebral palsy are detected, and for mental health screens, how well internalizing and externalizing disorders are detected. Predictive validity studies are not common but are desirable because they reflect how well screening test items and overall screening test performance measure enduring and meaningful dimensions of child development.

[Barbara Dente]

Criterion-related validity

This is the "acid test" of screening instrumentation and takes a unique form in screening test construction. Generally referred to as accuracy indices, criterion-related validity for screening tests include the following concepts:

- Sensitivity
- Specificity
- Positive predictive value
- Negative predictive value
- Hit rate

Sensitivity

In a random sample of children, if all were administered a diagnostic battery and categorized into the presence or absence of disabilities (e.g., by viewing eligibility for services under IDEA), some would be found to have disabilities. If screening tests were then given to the same group, ideally, all children with disabilities would score below cutoffs on the screen and thus be identified as needing referrals for diagnostic workups and special services. In reality, detection of disabilities is imperfect due to behavioral noncompliance, psychosocial malleability and age-related manifestations, and the brevity of screens. Thus, sensitivity, sometimes called co-positivity, is percentage of children with true problems correctly identified by a screening test (e.g., by failing, abnormal, or positive results). Ideally, 70% to 80% of those with difficulties should be identified. While this figure may seem low, many tests fail to attain this level of accuracy and none attain sensitivity that is substantially higher. More importantly, repeated screening is thought to improve detection rates over time.

Specificity

To continue the above example, most children in a random sample who are given diagnostic tests would be found to have normal development. Screening tests given to the same group would ideally identify all the children with typical development as normal (e.g., above cutoffs, passing or negative scores). Reality differs of course, and so specificity (or co-negativity) indicates the percentage of children without disabilities correctly identified, usually by passing or above cutoff scores on the screen. At least 70% to 80% of those with normal development should be correctly identified. Still, because there are many more children developing normally than not, specificity closer to 80% or higher is desirable.

Other Accuracy Indicators

Screening test research sometimes includes information on other accuracy indicators.

- Positive predictive value
- Negative predictive value
- Hit rate

Positive predictive value

Positive predictive value answers the question, to what extent does a suboptimal screening test score, reflect a true problem? If all children performing poorly on a screening test are pooled and administered diagnostic tests, at least a few will perform in the broad range of normal (because of the limits of specificity) and the rest will have disabilities. For example, if 9 out of 10 children with failing scores on screening tests are later found to have developmental diagnoses, the test’s positive predictive value is 9/10 or 90% meaning that for any screening test failure, there would be an 90% chance of a true developmental problem. In reality, positive predictive value is rarely 90% with values ranging from 30% to 50% being far more common (i.e., one of every two or three referrals will render a diagnosis. While this may seem troublingly inaccurate, the costs of over-referral (approximately $1000 for a comprehensive diagnostic evaluation) are substantially less than the cost of under-treatment, (a life-time loss to the child and society of more than $100,000 if needed early intervention is not offered).(Glascoe, Foster & Wolraich, 1997; Barnett & Escobar, 1990).

Over-referral

Also reassuring are results from a recent study showing that approximately 70% of children over-referred on developmental screening tests have numerous psychosocial risk factors and score on diagnostic measures of intelligence, language, and academic achievement, well below the 25th percentile (the point below which regular classroom instruction is less than optimally effective). Glascoe, 2001). This suggests that almost all children performing poorly on screening tests need at least some additional scrutiny and intervention and that a range of responses is desirable (e.g., Head Start, Title I, parent training, as well as special education and related services).

Negative predictive value

Negative predictive value is somewhat less commonly presented but involves determining the degree to which an optimal (above cutoff, passing or not-at-risk) score reflects typical or non-delayed development. For example, if 95 out of 100 children with passing scores on screening tests are later found on diagnostic testing to have typical development, the test’s negative predictive value is 95/100 or 95% meaning that for any passing score, there would be an 95% chance of a no developmental problem. Some measures also report over and under-referral rates. This reflects the proportion of the entire sample who should have been referred but were not correctly identified (under-referral rates) or should not have been referred (over-referral rates).

Hit rate

Hit rates are occasionally reported and are simply the total number of children for whom a screening test gave accurate information i.e.,co-positives and co-negatives are added together and then divided by the entire sample (co-positives + co-negatives+ false-positives + false negatives). Hit rates are an extremely misleading statistic and should not be used as an indicator of test accuracy. In the example shown in Figure 1, the hit rate is (70+16)/100 = 86%. Because there are far more co-negatives, specificity carries excessive weight in the computation of hit rates and as can be seen, the hit-rate is closer to the specificity index than to the sensitivity index. If in the above example, sensitivity were only 50% (10 children with disabilities correctly identified and 10 under-detected), the hit-rate would still remain deceptively attractive [(70+10)/100 = 80%] and mask serious flaws in accuracy.

Utility

Less of a psychometric construct and more a function of practical attributes, screens should be studied for their usefulness to diverse professionals in varied settings. Such studies often address length of administration and scoring, acceptability to parents and children, readability, amount of training required, cost of administration in terms of professional time to deliver the measure, score and interpret it, and descriptions of other amenities helpful to specific applications (e.g., ability to aggregate results for program evaluation, availability of growth indicators for use in plotting progress over time, etc.).

Prescreening

In an effort to conserve educational and health care dollars, it is obviously desirable to select measures with a high degree of positive predictive value. Given the subtlety and gradations of developmental outcomes, high positive predictive value remains elusive. Nevertheless, positive predictive value by administering a second screening test or by using part of a screen (e.g., a subtest) as a prescreen. Prescreening tests are extremely brief measures with a high degree of sensitivity but limited specificity. Prescreens are administered routinely and are followed by screening tests only when children fail the prescreen. Although prescreening can simply compound error and lead to under-referrals, accurate prescreening improves detection rates, and saves considerable time, since prescreens reduce, often by one-half to two-thirds, the numbers of children requiring complete screening.

[10-7B]

Back to the subject

Copyright issues have traditionally been not given the importance they deserve. That's have been the case even in the US, let alone in less developed countries. When I was in school in Russia I remember many professiors who'd translate books from English to Russian and publish it as if they had written it themselves, under their own name. We as students would not mind it had the books been translated correctly.. but these "professors" did not even know English good enough!

Believe it or not, in British law publishing someone else's original copy work and claiming you have made it (known as plagiarism and completely different from copyright infringement) is a criminal offence. For the most part, the criminal law is only used for commercial copyright infringement with one exception, and an offence is committed when knowing or reasonably suspecting that the files are illegal copies, and without the permission of the copyright owner, a person:

• makes unauthorised copies e.g. burning music files or films on to CD-Rs or DVD-Rs;
• distributes, sells or hires out unauthorised copies of CDs, VCDs and DVDs;
• on a larger scale, distributes unauthorised copies as a commercial enterprise on the internet;
• possesses unauthorised copies with a view to distributing, selling or hiring these to other people;
• while not dealing commercially, distributes unauthorised copies of software packages, books, music, games, and films on such a scale as to have a measurable impact on the copyright owner's business;
• publishing someone else's original copy work and claiming you have made it
• certain copyrights allow Archival copies of software to be made however these are not to be distributed.

The penalties for these "copyright infringement" offences depend on the seriousness of the offences:

• before a magistrates' Court, the penalties for distributing unauthorised files are a maximum fine of £5,000 and/or six months imprisonment;
• in the Crown Court, the penalties for distributing unauthorised files are an unlimited fine and/or up to 10 years imprisonment.

Also note §24 Copyright and Related Rights Regulations 2003 which creates a range of offences relating to the distribution of any device, product or component which is primarily designed, produced, or adapted for the purpose of enabling or facilitating the circumvention of effective technological measures. When this is for non-commercial purposes, it requires there to be a measurable effect on the rights holder's business.

[florida357]

I really hated this book.  It was the book for people who don't usually read but want to sound smart.

It wasn't awfully written, a small notch below your average John Grisham novel, but it got negative points for all the undeserved hype.

[dsetterl]

I was a medieval studies major (yikes I know) in UG, and I believe books like Dan Brown serve an important role in society. While this book was not mind-blowing it was entertaining and thought provoking. I also believe that this book probably caused more people to go and buy Holy Blood, Holy Grail. It is common knowledge that Dan Brown based his story around this idea. Does it make in unoriginal? Sure. But it was not meant to read as an academic, informative source. D. B's book's purpose was meant to entertain. I mean should the Jew's sue George Lucas for Raiders of the Lost Arc? (Not the best example by any means) I think it comes off as more of a tribute to them and their work. I mean no one (except dorks like me) would have known their book had even existed.

[dsetterl]

FYI- The "Christian idea" of the holy grail is usually attributed to Chretien de Troyes in his story Perceval.  Before him the grail finds its beginning in Norse and Celtic oral traditions and it is from here that Chretien lifted this idea and Christianized a common pagan theme.

[dsetterl]

Rather, they are alleging that Brown's book copies not only the basic themes of their book, but that it also copies their book's architecture and basic narritive structure.

Their book is a non-fiction book. What themes would be taken from it? How would the narrative structure apply? They read very differently. This lawsuit was ridiculous. I hope they made enough money from boosted sales to cover court expenses.

[STATA]

Back to the subject

Copyright issues have traditionally been not given the importance they deserve. That's have been the case even in the US, let alone in less developed countries. When I was in school in Russia I remember many professiors who'd translate books from English to Russian and publish it as if they had written it themselves, under their own name. We as students would not mind it had the books been translated correctly.. but these "professors" did not even know English good enough!

Believe it or not, in British law publishing someone else's original copy work and claiming you have made it (known as plagiarism and completely different from copyright infringement) is a criminal offence. For the most part, the criminal law is only used for commercial copyright infringement with one exception, and an offence is committed when knowing or reasonably suspecting that the files are illegal copies, and without the permission of the copyright owner, a person:

• makes unauthorised copies e.g. burning music files or films on to CD-Rs or DVD-Rs;
• distributes, sells or hires out unauthorised copies of CDs, VCDs and DVDs;
• on a larger scale, distributes unauthorised copies as a commercial enterprise on the internet;
• possesses unauthorised copies with a view to distributing, selling or hiring these to other people;
• while not dealing commercially, distributes unauthorised copies of software packages, books, music, games, and films on such a scale as to have a measurable impact on the copyright owner's business;
• publishing someone else's original copy work and claiming you have made it
• certain copyrights allow Archival copies of software to be made however these are not to be distributed.

The penalties for these "copyright infringement" offences depend on the seriousness of the offences:

• before a magistrates' Court, the penalties for distributing unauthorised files are a maximum fine of £5,000 and/or six months imprisonment;
• in the Crown Court, the penalties for distributing unauthorised files are an unlimited fine and/or up to 10 years imprisonment.

Also note §24 Copyright and Related Rights Regulations 2003 which creates a range of offences relating to the distribution of any device, product or component which is primarily designed, produced, or adapted for the purpose of enabling or facilitating the circumvention of effective technological measures. When this is for non-commercial purposes, it requires there to be a measurable effect on the rights holder's business.

In the US the major problem appears to be self-plagiarism. It is the reuse of significant, identical, or nearly identical portions of one's own work without acknowledging that one is doing so or without citing the original work. Articles of this nature are often referred to as multiple publications. Typically, high public-interest texts are not a subject of self-plagiarism; however, the authors should not violate copyright where applicable. "Public-interest texts" include such material as social, professional, and cultural opinions usually published in newspapers and magazines. In academic fields, self-plagiarism is a problem when an author reuses portions of his or her own published and copyrighted work in subsequent publications, but without attributing the previous publication. Identifying self-plagiarism is often difficult because of legal issues regarding fair use. Some professional organizations like the Association for Computing Machinery (ACM) have created policies that deal specifically with self-plagiarism. As compared to plagiarism, self-plagiarism is not yet very well-regulated. Some universities and editorial boards chose to not regulate it at all; they consider the term self-plagiarism oxymoronic since a person cannot be accused of stealing from himself.

[p i l]

[...] from both cohort and case-control studies always reflect true associations which can be universally generalized. Epidemiological research is, to a large extent, of an observational character as opposed to experimental research. One should not forget that observational epidemiological studies are subject to the influence of factors over which the investigators most often do not have full control, and that findings from these studies are less reliable than those of studies with an experimental research design. It is therefore imperative that findings from analytical epidemiological studies are critically scrutinized before any judgement of causality is made. Furthermore, findings from one single epidemiological study only exceptionally provide conclusive evidence of a causal relationship between exposure and disease.

LOL! I know what you mean