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can do in a few seconds what takes minutes or hours by hand, the use of computer statistical software is recommended and encouraged. However, computers are inherently stupid, and if they are not given the correct instructions, they will display on screen a result which is meaningless in relation to the problem being solved. It is vitally important, therefore, to learn how to enter relevant data and instructions correctly and interpret computer output to ensure that the computer has done what you wanted it to do. Throughout the book, examples of output from SPSS are used to show how computers can display the results of analyses, and how these results can be interpreted.

      This text is unashamedly oriented toward experimental science and the idea that things can be measured objectively or in controlled circumstances. This is a different emphasis from books which are oriented toward qualitative science, where descriptions of how people feel or perceive themselves or others are of greater importance than quantitative measures such as nutrient intake or blood pressure. Both approaches have their strengths and weaknesses, and it is not my intention to argue their relative merits here.

Illustration of a friendly statistician.

      The examples are taken mainly from studies in nutrition and dietetics. The aim is to provide material relevant to the reader’s working life, be they students, researchers, tutors, or practicing nutrition scientists or dietitians.

      Learning Objectives

      After studying this chapter you should be able to:

       Describe the process called the scientific method: the way scientists plan, design, and carry out research

       Define different types of logic, hypotheses, and research designs

       Know the principles of presenting data and reporting the results of scientific research

       What can I know?

       —Immanuel Kant, philosopher

      The need to know things is essential to our being in the world. Without learning we die. At the very least, we must learn how to find food and keep ourselves warm. Most people, of course, are interested in more than these basics, in developing lives which could be described as fulfilling. We endeavour to learn how to develop relationships, earn a livelihood, cope with illness, write poetry (most of it pretty terrible), and make sense of our existence. At the core of these endeavours is the belief that somewhere there is the ‘truth’ about how things ‘really’ are.

      Much of the seeking after truth is based on feelings and intuition. We may ‘believe’ that all politicians are corrupt (based on one lot of evidence), and at the same time believe that people are inherently good (based on a different lot of evidence). Underlying these beliefs is a tacit conviction that there is truth in what we believe, even though all of our observations are not consistent. There are useful expressions like: ‘It is the exception that proves the rule’ to help us cope with observations that do not fit neatly into our belief systems. But fundamentally, we want to be able to ‘prove’ that what we believe is correct (i.e. true), and we busy ourselves collecting examples that support our point of view.

      Karl Popper puts it this way:

       We can learn from our mistakes. The way in which knowledge progresses, and especially our scientific knowledge, is by unjustified (and unjustifiable) anticipations, by guesses, by tentative solutions to our problems, by conjectures. These conjectures are controlled by criticism; that is, by attempted refutations, which include severely critical tests. Criticism of our conjectures is of decisive importance: by bringing out our mistakes it makes us understand the difficulties of the problems which we are trying to solve. This is how we become better acquainted with our problem, and able to propose more mature solutions: the very refutation of a theory – that is, of any serious tentative solution to our problem – is always a step forward that takes us nearer to the truth. And this is how we can learn from our mistakes.

       From ‘Conjectures and Refutations. The Growth of Scientific Knowledge’ [1].

      Consider the question: ‘What do you understand if someone says that something has been proven “scientifically”?’ While we might like to apply to the demonstration of scientific proof words like ‘objective’, ‘valid’, ‘reliable’, ‘measured’, ‘true’, and so on, the common

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