Part 2 book “Research methods in health” has contents: Sample selection and group assignment methods in experiments and other analytic method, questionnaire design, techniques of survey interviewing, unstructured and structured observational studies, and other contents. | Chapter 10 Quantitative research: experiments and other analytic methods of investigation Chapter contents Introduction 235 The experimental method 235 Internal and external validity 238 Reducing bias in participants and the investigating team 241 Blind experiments 243 The RCT in health care evaluation 243 Other analytic methods of investigation 249 Before–after study with non-randomised control group 251 After-only study with non-randomised control group 251 Time series studies using different samples (historical controls) 252 Geographical comparisons 252 People acting as own controls 253 Within-person, controlled site study 253 Threats to the validity of causal inferences in other analytic studies Summary of main points Key questions Key terms Recommended reading 253 254 254 255 255 234 Chapter 10╇ Quantitative research: experiments and other analytic methods 235 Introduction T he accurate assessment of the outcome, or effects, of an intervention necessitates the careful manipulation of that intervention (experimental variable), in controlled conditions, and a comparison of the group receiving the intervention with an equivalent control group. It is essential that systematic errors (bias) and random errors (chance) are minimised. This requirement necessitates carefully designed, rigorously carried out studies, using reliable and valid methods of measurement, and with sufficiently large samples of participants who are representative of the target population. This chapter describes the range of methods available, along with their strengths and weaknesses. The experimental method T he experiment is a situation in which the independent variable (also known as the exposure, the intervention, the experimental or predictor variable) is carefully manipulated by the investigator under known, tightly defined and controlled conditions, or by natural occurrence. At its most basic, the experiment consists of an .
