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RESEARCH METHOD COHEN ok

RESEARCH METHOD COHEN ok RESEARCH METHOD COHEN ok

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PROCEDURES IN EX POST FACTO RESEARCH 271 explanations for the empirical outcomes of the study. A researcher has thus to beware of accepting the first likely explanation of relationships in an ex post facto study as necessarily the only or final one. A well-known instance to which reference has already been made is the presumed relationship between cigarette smoking and lung cancer. Health officials have been quick to seize on the explanation that smoking causes lung cancer. Tobacco firms, however, have put forward an alternative hypothesis – that both smoking and lung cancer are possibly the result of a third, as yet unspecified, factor, i.e. the possibility that both the independent and dependent variables are simply two separate results of a single common cause cannot be ignored. Chapter 12

13 Experiments, quasi-experiments, single-case research and meta-analysis Introduction The issue of causality and, hence, predictability has exercised the minds of researchers considerably (Smith 1991: 177). One response has been in the operation of control, anditfindsitsapotheosis in the experimental design. If rival causes or explanations can be eliminated from a study then clear causality can be established; the model can explain outcomes. Smith (1991: 177) claims the high ground for the experimental approach, arguing that it is the only method that directly concerns itself with causality; this, clearly is contestable, as we make clear in Part Three of this book. In Chapter 12, we described ex post facto research as experimentation in reverse in that ex post facto studies start with groups that are already different with regard to certain characteristics and then proceed to search, in retrospect, for the factors that brought about those differences. We then went on to cite Kerlinger’s description of the experimental researcher’s approach: If x, theny; iffrustration,thenaggression... the researcher uses some method to measure x and then observes y to see if concomitant variation occurs. (Kerlinger 1970) The essential feature of experimental research is that investigators deliberately control and manipulate the conditions which determine the events in which they are interested, introduce an intervention and measure the difference that it makes. An experiment involves making a change in the value of one variable – called the independent variable – and observing the effect of that change on another variable – called the dependent variable. Using a fixed design, experimental research can be confirmatory, seeking to support or not to support a null hypothesis, or exploratory, discoveringtheeffectsofcertain variables. An independent variable is the input variable, whereas the dependent variable is the outcome variable – the result; for example, Kgaile and Morrison (2006) indicate seven independent variables that have an effect on the result (the effectiveness of the school) (Box 13.1). In an experiment the post-test measures the dependent variable, and the independent variables are isolated and controlled carefully. Imagine that we have been transported to a laboratory to investigate the properties of a new wonder-fertilizer that farmers could use on their cereal crops, let us say wheat (Morrison 1993: 44–5). The scientist would take the bag of wheat seed and randomly split it into two equal parts. One part would be grown under normal existing conditions – controlled and measured amounts of soil, warmth, water and light and no other factors. This would be called the control group. The other part would be grown under the same conditions – the same controlled and measured amounts of soil, warmth, water and light as the control group, but, additionally,thenewwonderfertilizer. Then, four months later, the two groups are examined and their growth measured. The control group has grown half a metre and each ear of wheat is in place but the seeds are small. The experimental group, by contrast, has grown half ametreaswellbuthassignificantlymoreseeds on each ear, the seeds are larger, fuller and more robust.

PROCEDURES IN EX POST FACTO <strong>RESEARCH</strong> 271<br />

explanations for the empirical outcomes of the<br />

study. A researcher has thus to beware of accepting<br />

the first likely explanation of relationships in<br />

an ex post facto study as necessarily the only<br />

or final one. A well-known instance to which<br />

reference has already been made is the presumed<br />

relationship between cigarette sm<strong>ok</strong>ing and lung<br />

cancer. Health officials have been quick to seize on<br />

the explanation that sm<strong>ok</strong>ing causes lung cancer.<br />

Tobacco firms, however, have put forward an<br />

alternative hypothesis – that both sm<strong>ok</strong>ing and<br />

lung cancer are possibly the result of a third, as yet<br />

unspecified, factor, i.e. the possibility that both the<br />

independent and dependent variables are simply<br />

two separate results of a single common cause<br />

cannot be ignored.<br />

Chapter 12

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