CAUSAL AND COMPARATIVE RESEARCH: DEFINITION AND PURPOSE
-Causal-comparative research is sometimes treated as a type of descriptive research since it describes conditions that already exist.
• -Causal comparative research attempts to determine reasons, or causes, for the existing condition • -In causal-comparative or ,ex-post facto, research the researcher attempts to determine the cause, or reason, for preexisting differences in groups of individuals o -Such research is referred to as ex post facto (Latin for “after the fact”) since both the effect and the alleged cause have already occurred and must be studied in retrospect • -The basic causal-comparative approach involves starting with an effect and seeking possible causes -The basic approach starts with cause and investigates its effects on some variable • -The basic approach is sometimes referred to as retrospective causal-comparative research (since it starts with effects and investigates causes) • -The variation as prospective causal-comparative research (since it starts with causes and investigates effects) • -Retrospective causal-comparative studies are far more common in educational research • -Causal-comparative studies attempt to identify cause-effect relationships; correlational studies do not • -Causal-comparative studies typically involve two (or more) groups and one independent variable, whereas correlational studies typically involve two or more variables and one group • -Causal-comparative studies involve comparison, correlational studies involve relationship -Neither method provides researchers with true experimental data • -Causal-comparative and experimental research both attempt to establish cause-effect relationships and both involve comparisons. • -Experimental study the researcher selects a random sample and then randomly divides the sample into two or more groups -Groups are assigned to the treatments and the study is carried out • -Individuals are not randomly assigned to treatment groups because they already were selected into groups before the research began • -Experimental research the independent variable is manipulated by the researcher, whereas in causal-comparative research, the groups are already formed and already different on the independent variable • -Independent variables in causal-comparative cannot be manipulated, should not be manipulated, or simply are not manipulated but could be • -Not possible to manipulate organismic variables such as age or gender • -Ethical considerations often prevent manipulation of a variable that could be manipulated but should not be -If the nature of the independent variable is such that it may cause physical or mental harm to participants, the ethics of research dictate that it should not be manipulated -Figure 12.1 shows independent variables used to compare two or more levels of a given variable -Students with high anxiety could be compared to students with low anxiety on attention span, or the difference in achievement between first graders who attended preschool and first graders who did not could be examined. -Experimental studies are costly in more ways than one and should only be conducted when there is good reason to believe the effort will be fruitful • -Causal comparative studies help to identify variables worthy of experimental investigation • -Despite many key advantages, causal comparative research does have some serious limitations that should also be kept in mind -Since the independent variable has already occurred, the same kinds of controls cannot be exercised as in an experimental study • -Caution must be applied in interpreting results
• -The alleged cause of an observed effect may in fact be the effect itself, or there may be a third variable -For example, a researcher hypothesized that self-concept is a determinant of reading...