Critical Thinking: Components of Causal Studies

CRITICAL THINKING COMPONENTS OF CAUSAL STUDIES Causal Hypothesis: Everything starts with a causal hypothesis. A causal hypothesis is a supposition or theory about how things interact, specifically, on whether one thing causes another. The purpose of causal studies is to confirm or reject any given causal hypothesis. For example, a causal hypothesis we might want to seek evidence for the idea that inhaling chalk dust causes asthma. Cause: A cause is something that is thought to bring about something else. For example, we might think that inhaling chalk dust causes asthma. Given this causal hypothesis the cause would be the inhaling of chalk dust. Causal factor: Almost all the time any given effect is caused by an interaction of many factors. As a result, we cannot say that any one thing, such as inhaling chalk dust, is the actual cause of cancer in an individual. Instead we can usually only show that something, such as inhaling chalk dust, is a causal factor in producing a certain effect in a group of people. Effect: An effect of something is the result brought about by that thing or cause. For example, we might think that asthma is an effect of inhaling chalk dust. Causal Studies: Causal studies are studies designed to test a causal hypothesis. For example, we might create a causal study to provide evidence for the hypothesis that inhaling chalk causes asthma. Causal studies look for causal factors in studies of groups or populations of people. COMPONENTS OF A CAUSAL STUDY Experimental Group: The experimental group is the group of individuals that either (1) have been subjected to the supposed causal agent already, (nonexperimental cause-to-effect studies), or (2) display the effect being studied (nonexperimental effect-to-cause studies), or (3) are subjected to the supposed cause being studied (controlled causeto-effect studies). Control Group: The control group is a group of individuals that have not been exposed to the supposed cause or do not display the supposed effect. When selecting the control group it is important for the control group to be as much like the experimental group as possible, with the exception of either having been exposed to the cause or displaying the effect. For example, if we were going to use a controlled cause-to-effect study to test the hypothesis that inhaling chalk dust contributes to asthma, we would select a group of people who are representative of the general population, and then we would divide the group into an experimental group and a control group. Then we would expose the experimental group to the suspected causal agent. Frequency: The frequency of either the experimental or control group is the percentage of the group that displays the effect. For example, in a study attempting to correlate chalk intake with asthma, the frequency of the experimental group would be the percentage of the experimental group that showed the effect (lets say 50%). In contrast, the frequency of the control group would be the percentage of people in the control group that display the effect at the end of the study. Difference: The difference between the frequencies of the experimental group and the control group is what is used to evaluate the causal hypothesis correlating the supposed causal factor and the effect. The difference is the difference between the percentages of the frequencies of the control and experimental group. For example, if 50% of the experimental group develop asthma after having inhaled a certain amount of chalk dust, and 20% of the control group develop asthma even without the chalk dust, the difference would be 30%. Statistical Significance: To say that certain study results (i.e. certain difference in frequencies) is statistically significant is to say that it would be unreasonable to attribute the difference to the results of chance. To assess statistical significance you can use a table that correlates the difference in frequencies with the size of the control group.