Читать книгу Demystifying Research for Medical and Healthcare Students - John L. Anderson - Страница 19

1 Cross‐sectional studies: These are the commonest type of studies used in quantitative research. They involve taking a ‘snapshot’ of what is happening in a group or a population at a particular point in time. The most widely used approach is the survey. These are termed ‘retrospective’ studies, because what we are enquiring about has already happened – it is in the past. We shall look at these in depth later in Chapters 8 and 9.

2 Case‐control studies: Case‐control studies are commonly used in epidemiological research when we want to check what factors cause a disease that we are concerned about. These are a pleasingly neat design. We identify and recruit a group of people with a disease, then we identify and recruit a group of people who are similar in almost every respect – except that they do not have that disease. Then we measure the extent to which each group have been exposed to a suspected causal factor and measure the difference between the two groups. If the ‘Cases’ score higher than the ‘Controls’, then we conclude that the factor we are comparing them on is indeed a suspected contributory factor for that disease or condition. Neat – eh? These are also termed ‘retrospective’ studies because what we are enquiring about has already happened – it is in the past. We shall look at these in depth later in Chapter 7.

3 Cohort studies: The term cohort is a posh word for a group. It comes from the Latin ‘cohors’ which was a group of soldiers in a Roman Legion – a platoon, sort of. In cohort studies, we recruit a group of people and follow them up over a period of time. We may choose people for a specific reason or a wide range of reasons and record significant events as they arise. These are different to the last two approaches in that they are not ‘retrospective’ studies, because we are interested in what will happen – in the future. They are what we call ‘prospective’ studies. We shall look at these in depth in Chapter 6.