Scientific method and design of experiments

Science is a systematized body of knowledge derived from observation and experiment. Scientists carry out experiments, make observations and attempt to explain the results these tentative explanations are called hypotheses and their validity is tested by systematically forming and rejecting alternative explanations. 

Some branches of chemistry are designed to provide fundamental information, rather than to test a particular hypothesis for example, the purification and characterization of a newly discovered naturally occurring molecule. In contrast, an experiment is a contrived situation designed to test one or more hypothesis under conditions controlled by the investigator. Any hypothesis that cannot be rejected from the results of an experiment is provisionally accepted. This sieve effect leaves us with a set of current explanations for our observations. These explanations are not permanent and may be rejected on the basis of a future investigation. A hypothesis that has withstood many such tests and has been shown to allow predictions to be made is known as a theory, and a theory may generate such confidence through its predictive abilities to be known as a law (Fig. 10.1). 

Observations are a prelude to experimentation, but they are preconditioned by a framework of peripheral knowledge. While there is an element of luck in being at the right place and time to make important observations, as Pasteur stated, chance favours only the prepared mind . A fault in scientific method is that the design of the experiment and choice of method may influence the outcome - the decisions involved may not be as objective as some scientists assume. Another flaw is that radical alternative hypotheses may be overlooked in favour of a modification to the original hypothesis, and yet just such leaps in thinking have frequently been required before great scientific advances. 

No hypothesis can ever be rejected with certainty. Statistics allow us to quantify as vanishingly small the probability of an erroneous conclusion, but we are nevertheless left in the position of never being 100% certain that we have rejected all relevant alternative hypotheses, nor 100% certain that our decision to reject some alternative hypotheses was correct However, despite these problems, experimental science has yielded and continues to yield many important findings. 

The fallibility of scientific facts is essential to grasp. No explanation can ever be 100% certain as it is always possible for a new alternative hypothesis to be generated. Our understanding of chemistry changes all the time as new observations and methods force old hypotheses to be retested. 

Hypothesis - One possible explanation for an observed event. A mechanistic hypothesis is one based on some intuition about the mechanism underlying a phenomenon. 

Mathematical model - an algebraic summary of the relationship between the variables in a system. 

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Making and recording measurements SI units and, their use Scientific method and design of experiments ... 

The scientific method was designed to protect us from these errors of projection. A scientific experiment is an exercise in the elucidation of cause and the best experiments unmask false causation as much as they demonstrate true causation. In so far as our new dream theory is true, we can predict that brain activation of... 

As we have seen, both the scientific method and the statistical method are designed to prove a claim false rather than true. In drug testing, the statistical experiment is designed to reject the null hypothesis — the hypothesis of lack of efficacy, or that there is no difference between the treatments being tested. Table 25.1 mentioned above is applied to the null hypothesis. 

In this first chapter of your study of chemistry you will learn more about the importance of observation and accurate, precise measurement in medical practice and scientific study. You will also study the scientific method, the process of developing hypotheses to explain observations, and the design of experiments to test those hypotheses. 

Fisher RA (1925), Statistical Methods for Research Workers, Hafner Publishing Co., New York, NY, USA, re-issued (1990) as Statistical Methods, Experimental Design, and Scientific Inference A Re-issue of Statistical Methods for Research Workers, The Design of Experiments, and Statistical Methods and Scientific Inference (Ed. Bennett JH), Oxford University Press, Oxford, UK. 

It IS worth remembering that a theory can never be proven correct It can only be proven incor rect incomplete or inadequate Thus theories are always being tested and refined As important as anything else in the scientific method is the testable hypothesis Once a theory is proposed experiments are designed to test its validity If the results are con sistent with the theory our belief in its soundness is strengthened If the results conflict with it the theory IS flawed and must be modified Section 6 7 describes some observations that support the theory that car bocations are intermediates in the addition of hydro gen halides to alkenes... 

Gart, J. J., Krewski, D., Lee, P. N., Tarone, R. E. and Wahrendorf, J. (1986). The design and analysis of long-term animal experiment, in Statistical Methods in Cancer Research, Vol. III. IARC Scientific Publication No. 79. International Agency for Research on Cancer Lyon. 

The scientific research method consists of a cyclic sequence of experimental and logical steps designed to yield knowledge about the world by using conjecture and appeals to experience. The first step in the sequence is to divide the world into a conveniently sized part called the study system and a complementary part called the environment. A study system and its complement are created by and for the convenience of the investigator only. A study system can be of any size and type as long as it is known where in the universe it comes from and exactly where it fits in it. 

It is possible to conduct animal studies in an infinite number of ways. Although individually designed studies are often scientifically sound, and in many cases serve a particular purpose very well, they pose problems in a regulatory context. Free movement of chemicals between countries is based on the mutual acceptance of the risk evaluation made by each country and this, in turn, relies on the mutual acceptance of the data generated when testing the chemicals. Experience has shown this acceptance to be extremely difticult, if chemicals have been tested by different methods. 

Recent decades have seen the emergence of a novel approach to scientific research, based on the exploitation of fast electronic digital computers. Computation provides a method of investigation which transcends the traditional division between theory and experiment. Computer-assisted simulation and design may afford a solution to complex problems which would otherwise be intractable to theoretical analysis, and may also provide a viable alternative to difficult or costly laboratory experiments. Though stemming from Theoretical Chemistry, Computational Chemistry is a field of research... 

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