During the last presidential campaign, the Gallup organization surveyed a random sample of 30 registered Democrats in January, another 30 in February, and yet another 30 in March. All 90 Democrats were asked to “rate the chances of the Democrats winning the presidential race in your state.” The responses and their numerical codes were Excellent (4), Good (3), Fair (2), and Poor (1).

Do these data allow us to infer that Democrats’ ratings of their chances of winning the presidency changed over the 3-month period?