Analysis by Competing Hypothesis - SlideShare
Structured Analysis of Competing Hypotheses | …
Analysis of Competing Hypotheses (ACH) ..
Consider the clinical trial outlined above in which three competing treatments for joint pain are compared in terms of their mean time to pain relief in patients with osteoarthritis. Because investigators hypothesize that there may be a difference in time to pain relief in men versus women, they randomly assign 15 participating men to one of the three competing treatments and randomly assign 15 participating women to one of the three competing treatments (i.e., stratified randomization). Participating men and women do not know to which treatment they are assigned. They are instructed to take the assigned medication when they experience joint pain and to record the time, in minutes, until the pain subsides. The data (times to pain relief) are shown below and are organized by the assigned treatment and sex of the participant.
In statistics, refers to the process of choosing between competing hypotheses about a probability distribution, based on observed data from the distribution. It’s a core topic and a fundamental part of the language of statistics.
Analysis of Competing Hypotheses (ACH): Free Download …
The competing hypothesis is that giraffe necks evolved as a result of sexual selection. Even though naturalists have long-recognized that male giraffes often swing their necks to batter each other with their stout ossicones - Darwin even mentioned it in passing in Descent of Man - this habit was not thought to be especially relevant to giraffe evolution until a 1996 paper by Robert Simmons and Lue Scheepers entitled "Wining by a Neck: Sexual Seletion in the Evolution of Giraffe." Citing the observation that many giraffes they observed fed at a lower level than they expected, Simmons and Scheepers argued that a long neck did not confer that much of a feeding advantage. The competition between males, which they stated had longer and stronger necks, had driven the evolution of the giraffe neck, with female giraffes somehow carried along as sexual selection among males kept pushing the limits of neck length.
The standard hypothesis, which is an extension of the argument Darwin outlined in 1872, is that competition for food drove the evolution of elongated necks. Through competition for nutritious browse, natural selection would have resulted in the evolution of a giraffe able to reach otherwise unexploited resources above the heads of other herbivores. The idea that giraffes gain such a benefit was supported by one of the few experimental studies to look at this question. As illustrated by Elissa Cameron and Johan du Toit in a 2007 study of giraffe feeding ecology, it was found that lower-level herbivores deplete the abundance and quality of browse available to giraffes. By excluding browsers from feeding on certain Acaia trees, the scientists were able to measure just how much of a tree's foliage competing herbivores scarf up, and it became apparent that giraffes would definitely get the most from each mouthful by browsing high when low- and mid-level browse had been cleared away. Giraffes can feed at a variety of levels, and this ability to reach high during times of tough competition certainly provides them with an advantage.
Analysis of Competing Hypothesis (ACH) | Brunel …
If the necks of modern giraffes are at least partially attributable to a shift in function, then our ability to answer the question of giraffe evolution cannot be based upon living animals alone. In order to test their preferred sexual selection idea Simmons and Altwegg suggest going back to the fossil record to see when giraffes evolved the blunt ossicones males use in their competitions and how this corresponds to neck length. If the evolution of blunt ossicones tracks neck elongation, they hypothesize, then this might be an indicator that head-swinging contests had something to do with the neck elongation (while the browsing hypothesis would have more to do with detecting a relationship between neck and leg length which would have pushed giraffes over the heads of competing browsers). Correlation does not imply causation - even if the evolution of blunt, vertical ossicones and long necks coincided, that does not mean that the two are evolutionarily bound together - but by investigating these questions scientists would add a much-needed historical angle to research into giraffe necks.
Simmons and co-author R. Altwegg have just responded to this study in a new Journal of Zoology paper, and in surveying the debate they state that neither the food competition nor the necks-for-sex hypothesis may be able to provide a comprehensive explanation for giraffe evolution. Although they dispute the findings of Mitchell, van Sittert, and Skinner - arguing that the data collected by the other team actually represents a significant disparity between males and females triggered by sexual selection - they rightly note that most of what has been said about giraffe necks has depended upon the anatomy and behavior of living animals. The arguments and experiments about the necks of living giraffes have more to do with the evolutionary pressures which are maintaining the form of the giraffe, but they may not be able to tell us very much about how long necks evolved in the first place.
The Open Source Analysis of Competing Hypotheses Project
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-there are no other competing hypothesis
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ACH - Analysis of Competing Hypothesis | AcronymAttic
The exchange between Mivart and Darwin did nothing to resolve the question of how giraffes had evolved. Proposing plausible adaptive scenarios was easy, but actually testing them has been another matter altogether. Even now, after nearly a century and a half since the exchange between Darwin and Mivart, the evolution of the giraffe's peculiar neck remains contested, and the scope of the present debate has been shaped by two competing evolutionary hypotheses.
Step-by-Step Outline of Analysis of Competing Hypotheses
Globalytica, LLC, an affiliate company of Pherson Associates, has developed several simple, but elegant, web-based tools that enhance an analyst’s critical thinking skills. This toolbox of computer-assisted analytic techniques allow analysts to generate multiple hypotheses, validate scenario indicators, and use the Analysis of Competing Hypotheses Methodology in a collaborative, web-based environment.
ACH2.0 Download Page - PARC, a Xerox company
General. Analysis of Competing Hypotheses, ACH, is a simple model for how to think about and fuse geospatial information into analytic problems. As we have included ACH in our geospatial analytic method, it takes the geospatial analyst through a process to make well-reasoned, analytical judgments using both non-geospatial and geospatial information. It is particularly useful for predictions of what is likely to happen in the future. It helps an analyst to minimize some of the cognitive limitations we discussed earlier. The key elements of ACH we are going to address in this exercise are:
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