Final answer:
An experiment without a control variable is poor science because c) there's nothing to compare the results to, making it impossible to confidently attribute differences in outcomes to the experimental treatment, rather than to other uncontrolled factors.
Step-by-step explanation:
An experiment that fails to include a control variable is poor science due to c. nothing to compare the results to. Control variables are critical in experimental design as they allow for a comparison between the experimental group and a baseline or standard condition. Without a control, any observed effects cannot be confidently attributed to the variable being tested, since there's no way to determine if the change is due to the experimental treatment or another factor.
A well-designed experiment includes control groups that receive a placebo treatment, which should have no effect on the response variable. This setup helps ensure that any differences in outcomes can be attributed to the treatments being tested rather than to other variables. Experimental designs also often involve blinding to control for experimenter bias, where the researcher's expectations could influence the results. Statistical analysis then confirms if any differences between groups are significant and not due to chance. Without a control group, meaningful comparisons and interpretations are jeopardized, compromising the reliability and validity of the findings.