10.42 Graphic warnings, sugary beverages, and hypothesis testing: Researchers asked soda drinkers to view either the logo for their favorite soda or a graphic warning demonstrating the harmful effects of sugary beverages (e.g., tooth decay, obesity; Donnelly et al., 2018). They found that those participants who saw the warnings reported significantly greater negative moods than those who saw the logos, “(graphic warning: M =−2.13, SD = 1.63; no warning: M = 2.29, SD = 1.47), t(200) = 20.18, p < 0.001, d = 2.84, ” and reported a higher level of “intention to purchase water (graphic warning: M = 4.24, SD = 2.04; no warning: M = 2.72, SD = 1.72), t(200) = 5.71, p < 0.001, d = 0.80.”

a. Is it likely that the researchers used random selection? Explain.

b. Is it likely that the researchers used random assignment? Explain.

c. What is the independent variable, and what are its levels?

d. What is (are) the dependent variable(s)?

e. Which hypothesis test would the researchers use? Explain.

f. What did the researchers conclude with respect to each dependent variable (e.g., reject the null hypothesis or fail to reject the null hypothesis)? How can we know this just from the reported statistics? g. How large were these effects? Explain your answer. h. How could the researchers redesign this study so that they could use a paired-samples t test? i. The researchers reported: “The study was preregistered at ClinicalTrials.gov (https://clinicaltrials.gov/ct2/show/NCT02744859). Stimuli and data for this and both subsequent studies are available at the Open Science Framework (OSF; https://osf.io/rh8pv/)” (p. 1323). Why are preregistration and the sharing of materials at the Open Science Framework both ethical data practices?