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- Design of Experiments (DOE)
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This article evaluates the strengths and limitations of field experimentation. It first defines field experimentation and describes the many forms that field experiments take. It also interprets the growth and development of field experimentation. It then discusses why experiments are valuable for causal inference. The assumptions of experimental and nonexperimental inference are distinguished, noting that the value accorded to observational research is often inflated by misleading reporting conventions.
Experimentation: An Introduction to Measurement Theory and Experiment Design
Practicing and studying automated experimentation may benefit from philosophical reflection on experimental science in general. This paper reviews the relevant literature and discusses central issues in the philosophy of scientific experimentation. The first two sections present brief accounts of the rise of experimental science and of its philosophical study. The next sections discuss three central issues of scientific experimentation: the scientific and philosophical significance of intervention and production, the relationship between experimental science and technology, and the interactions between experimental and theoretical work.
The concluding section identifies three issues for further research: the role of computing and, more specifically, automating, in experimental research, the nature of experimentation in the social and human sciences, and the significance of normative, including ethical, problems in experimental science. Over the past decades the historical development of experimental science has been studied in detail. One focus has been on the nature and role of experiment during the rise of the natural sciences in the sixteenth and seventeenth centuries.
Earlier accounts of this so-called Scientific Revolution emphasized the universalization of the mathematical method or the mechanization of the world-view as the decisive achievement. In contrast, the more recent studies of sixteenth and seventeenth century science stress the great significance of a new experimental practice and a new experimental knowledge.
The story of the controversy of the latter with Thomas Hobbes, during the late s and early s, has become a paradigm of the recent historiography of scientific experimentation [ 1 ]. While Hobbes defended the 'old' axiomatic-deductive style of the geometric tradition, Boyle advocated the more modest acquisition of probable knowledge of experimental 'matters of fact'.
Simultaneously at stake in this controversy were the technical details of Boyle's air-pump experiments, the epistemological justification of the experimental knowledge and the social legitimacy of the new experimental style of doing science.
A more wide-ranging account of the role of experimentation in the natural sciences has been proposed by Thomas Kuhn [ 2 ]. He claims that the rise of modern physical science resulted from two simultaneous developments. On the one hand, a radical conceptual and world-view change occurred in what he calls the classical, or mathematical, sciences, such as astronomy, statics and optics. On the other, the novel type of Baconian, or experimental, sciences emerged, dealing with the study of light, heat, magnetism and electricity, among other things.
Kuhn argues that it was not before the second half of the nineteenth century that a systematic interaction and merging of the experimental and mathematical traditions took place. An example is the transformation of the Baconian science of heat into an experimental-mathematical thermodynamics during the first half of the nineteenth century.
At about the same time, the interactions between at first, mainly experimental science and technology increased substantially. Important results of this scientification of technology were chemical dye stuffs and artificial fertilizers. Starting in the second half of the nineteenth century, extensive experimentation also took root in various other sciences. This happened in medicine, in particular in physiology, somewhat later in psychology, and still later in the social sciences.
A characteristic feature of many experiments in those sciences is a strong reliance on statistical methods see, e. Alongside the actual practices of experimentation, a variety of authors--both philosophers and philosophy-minded scientists--have reflected upon the nature and function of scientific experiments. Among the better-known examples are Bacon's and Galileo's advocacy of the experimental method.
John Stuart Mill around the middle of the nineteenth century and Ernst Mach late nineteenth-early twentieth century provided some methodological and epistemological analyses of experimentation. Claude Bernard promoted and analyzed the use of the experimental method in medicine.
While those authors addressed some aspects of experimentation in their accounts of science, a substantial and coherent tradition in the philosophy of scientific experimentation did not yet arise.
Such a tradition did spring up in Germany, in the second half of the twentieth century. Within this German tradition two approaches may be distinguished. One developed Hugo Dingler's pioneering work [ 5 ]. Dingler emphasized the manipulation and intervention character of experimentation, and hence its kinship to technology. One of his aims was to show how the basic theoretical concepts of physics, such as length or mass, could be grounded in concrete experimental actions.
During the s and s, this part of Dingler's views was taken up and systematically developed by several other German philosophers, including Paul Lorenzen, Klaus Holzkamp and Peter Janich. More recently, the emphasis on the methodical construction of theoretical concepts in terms of experimental actions has given way to a more culturalistic interpretation of experimental procedures and results [ 6 ].
A second approach within the German tradition took its departure even more directly from the kinship between experiment and technology. In his work from the s, Habermas conceived of empirical-analytical science as 'anticipated technology', the crucial link being experimental action [ 7 ]. In the spirit of Karl Marx, Martin Heidegger and Herbert Marcuse, Habermas' aim was not merely to develop a theory of scientific knowledge but rather a critique of technocratic reason.
More recently, attempts have been made to connect this German tradition to Anglo-Saxon philosophy of experiment [ 8 , 9 ] and to contemporary social studies of science and technology [ 10 ].
In the English-speaking world, a substantial number of studies of scientific experimentation have been written since the mids. They resulted from the Kuhnian 'programs in history and philosophy of science'.
In their studies of historical or contemporary scientific controversies, sociologists of scientific knowledge often focused on experimental work e. An approach that remained more faithful to the history and philosophy of science idea started with Ian Hacking's argument for the relative autonomy of experimentation and his plea for a philosophical study of experiment as a topic in its own right [ 14 ].
More recently, several philosophers argue that a further step should be taken by combining the results of the historical and sociological study of experiment with more developed theoretical-philosophical analyses [ 18 ]. A mature philosophy of experiment, they claim, should not be limited to summing up its practical features but attempt to provide a systematic analysis of experimental practice and experimental knowledge.
The latter is often lacking in the sociological and historical literature on scientific experimentation. Looking at the specific features of experiments within the overall practice of science, there is one feature that stands out.
In order to perform experiments, whether they are large-scale or small-scale, experimenters have to intervene actively in the material world; moreover, in doing so they produce all kinds of new objects, substances, phenomena and processes.
More precisely, experimentation involves the material realization of the experimental system that is to say, the object s of study, the apparatus, and their interaction as well as an active intervention in the environment of this system. In this respect, experiment contrasts with theory even if theoretical work is always attended with material acts such as the typing or writing down of a mathematical formula. Hence, a central issue for a philosophy of experiment is the question of the nature of experimental intervention and production, and their philosophical implications.
To be sure, at times scientists devise and discuss so-called thought experiments [ 19 ]. However, such 'experiments'--in which the crucial aspect of intervention and production is missing--are better conceived as not being experiments at all but rather as particular types of theoretical argument, which may or may not be materially realizable in experimental practice.
Clearly, not just any kind of intervention in the material world counts as a scientific experiment. Quite generally, one may say that successful experiments require, at least, a certain stability and reproducibility, and meeting this requirement presupposes a measure of control of the experimental system and its environment as well as a measure of discipline of the experimenters and the other people involved in realizing the experiment.
Experimenters employ a variety of strategies for producing stable and reproducible experiments see, e. One such strategy is to attempt to realize 'pure cases' of experimental effects. He systematically varied a number of factors of his experimental system and examined whether or not they were relevant, that is to say, whether or not they had a destabilizing impact on the experimental process. Furthermore, realizing a stable object-apparatus system requires knowledge and control of the actual and potential interactions between this system and its environment.
Depending on the aim and design of the experiment, specific interactions may be necessary and hence required , allowed but irrelevant , or forbidden because disturbing. In response, he designed his experiment in such a way that terrestrial magnetism constituted an allowed rather than a forbidden interaction.
A further aspect of experimental stability is implied by the notion of reproducibility [ 9 ]. A successful performance of an experiment by the original experimenter is an achievement that may depend on certain idiosyncratic aspects of a local situation. Yet, a purely local experiment that cannot be carried out in other experimental contexts will, in the end, be unproductive for science.
However, since the performance of an experiment is a complex process, no repetition will be strictly identical to the original experiment and many repetitions may be dissimilar in several respects. For this reason, we need to specify what we take or require to be reproducible for instance, a particular aspect of the experimental process or a certain average over different runs.
Furthermore, there is the question of who should be able to reproduce the experiment for instance, the original experimenter, contemporary scientists, or even any scientist or human being.
Investigating these questions leads to different types and ranges of experimental reproducibility, which can be observed to play different roles in experimental practice. Laboratory experiments in physics, chemistry and molecular biology often allow one to control the objects under investigation to such an extent that the relevant objects in successive experiments may be assumed to be in identical states.
Hence, statistical methods are employed primarily to further analyze or process the data see, for instance, the error-statistical approach by Deborah Mayo [ 23 ]. In contrast, in field biology, medicine, psychology and social science, such a strict experimental control is often not feasible. To compensate for this, statistical methods in these areas are used directly to construct groups of experimental subjects that are presumed to possess identical average characteristics.
It is only after such groups have been constructed that one can start the investigation of hypotheses about the research subjects.
One can phrase this contrast in a different way by saying that in the former group of sciences statistical considerations mostly bear upon linking experimental data and theoretical hypotheses, while in the latter group it is often the case that statistics already play a role at the stage of producing the actual individual data.
The intervention and production aspect of scientific experimentation carries implications for several philosophical questions. A general lesson, already drawn by Bachelard, appears to be this: the intervention and production character of experimentation entails that the actual objects and phenomena themselves are, at least in part, materially realized through human interference.
Hence, it is not just the knowledge of experimental objects and phenomena but also their actual existence and occurrence that prove to be dependent on specific, productive interventions by the experimenters. This fact gives rise to a number of important philosophical issues. If experimental objects and phenomena have to be realized through active human intervention, does it still make sense to speak of a 'natural' nature or does one merely deal with artificially produced laboratory worlds?
If one does not want to endorse a fully-fledged constructivism, according to which the experimental objects and phenomena are nothing but artificial, human creations, one needs to develop a more differentiated categorization of reality. In this spirit, various authors e. These human-independent dispositions would then underlie and enable the human construction of particular experimental processes.
A further important question is whether scientists, on the basis of artificial experimental intervention, can acquire knowledge of a human-independent nature.
Some philosophers claim that, at least in a number of philosophically significant cases, such 'back inferences' from the artificial laboratory experiments to their natural counterparts can be justified. Another approach accepts the constructed nature of much experimental science, but stresses the fact that its results acquire a certain endurance and autonomy with respect to both the context in which they have been realized in the first place and later developments.
In this vein, Davis Baird [ 24 ] offers an account of 'objective thing knowledge', the knowledge encapsulated in material things, such as Watson and Crick's material double helix model or the Indicator of Watt and Southern's steam engine. Another relevant feature of experimental science is the distinction between the working of an apparatus and its theoretical accounts.
In actual practice it is often the case that experimental devices work well, even if scientists disagree on how they work. This fact supports the claim that variety and variability at the theoretical level may well go together with a considerable stability at the level of the material realization of experiments.
This claim can then be exploited for philosophical purposes, for example to vindicate entity realism [ 14 ] or referential realism [ 8 ]. Traditionally, philosophers of science have defined the aim of science as, roughly, the generation of reliable knowledge of the world.
Moreover, as a consequence of explicit or implicit empiricist influences, there has been a strong tendency to take the production of experimental knowledge for granted and to focus on theoretical knowledge. However, if one takes a more empirical look at the sciences, both at their historical development and at their current condition, this approach must be qualified as one-sided.
After all, from Archimedes' lever-and-pulley systems to the cloned sheep Dolly, the development of experimental science has been intricately interwoven with the development of technology [ 25 , 26 ]. Experiments make essential use of often specifically designed technological devices, and, conversely, experimental research often contributes to technological innovations.
Moreover, there are substantial conceptual similarities between the realization of experimental and that of technological processes, most significantly the implied possibility and necessity of the manipulation and control of nature. Taken together, these facts justify the claim that the science-technology relationship ought to be a central topic for the study of scientific experimentation.
One obvious way to study the role of technology in science is to focus on the instruments and equipment employed in experimental practice. Many studies have shown that the investigation of scientific instruments is a rich source of insights for a philosophy of scientific experimentation see, e.
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[PDF Download] Experimentation: An Introduction to Measurement Theory and Experiment Design
In the fast-moving digital world, even experts have a hard time assessing new ideas. They argue that if a company sets up the right infrastructure and software, it will be able to evaluate ideas not only for improving websites but also for new business models, products, strategies, and marketing campaigns—all relatively inexpensively. When building websites and applications, too many companies make decisions—on everything from new product features, to look and feel, to marketing campaigns—using subjective opinions rather than hard data. Companies should conduct online controlled experiments to evaluate their ideas. Potential improvements should be rigorously tested, because large investments can fail to deliver, and some tiny changes can be surprisingly detrimental while others have big payoffs.
Design of Experiments (DOE)
Practicing and studying automated experimentation may benefit from philosophical reflection on experimental science in general. This paper reviews the relevant literature and discusses central issues in the philosophy of scientific experimentation. The first two sections present brief accounts of the rise of experimental science and of its philosophical study. The next sections discuss three central issues of scientific experimentation: the scientific and philosophical significance of intervention and production, the relationship between experimental science and technology, and the interactions between experimental and theoretical work. The concluding section identifies three issues for further research: the role of computing and, more specifically, automating, in experimental research, the nature of experimentation in the social and human sciences, and the significance of normative, including ethical, problems in experimental science.
The term experiment is defined as the systematic procedure carried out under controlled conditions in order to discover an unknown effect, to test or establish a hypothesis, or to illustrate a known effect. When analyzing a process, experiments are often used to evaluate which process inputs have a significant impact on the process output, and what the target level of those inputs should be to achieve a desired result output. Experiments can be designed in many different ways to collect this information.
The books by Campbell and Stanley and Cook and Campbell are considered classic in the field of experimental design. The following is summary of their books with insertion of our examples. Problem and Background Experimental method and essay-writing Campbell and Stanley point out that adherence to experimentation dominated the field of education through the s Thorndike era but that this gave way to great pessimism and rejection by the late s. However, it should be noted that a departure from experimentation to essay writing Thorndike to Gestalt Psychology occurred most often by people already adept at the experimental tradition. Therefore we must be aware of the past so that we avoid total rejection of any method, and instead take a serious look at the effectiveness and applicability of current and past methods without making false assumptions. Replication Multiple experimentation is more typical of science than a once and for all definitive experiment!
Chemistry is the study of matter. Our understanding of chemical processes thus depends on our ability to acquire accurate information about matter. Often, this information is quantitative, in the form of measurements. In this lab, you will be introduced to some common measuring devices, and learn how to use them to obtain correct measurements, each with correct precision.
An experiment is a procedure carried out to support, refute, or validate a hypothesis. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs when a particular factor is manipulated. Experiments vary greatly in goal and scale, but always rely on repeatable procedure and logical analysis of the results. There also exists natural experimental studies.