The ecology club at a local high school took separate random samples of sophomores, juniors, and seniors to learn whether there are differences in attitudes toward recycling by grade level. Students...

The ecology club at a local high school took separate random samples of sophomores, juniors, and seniors to learn whether there are differences in attitudes toward recycling by grade level. Students were asked to respond yes or no to the question, “Do you regularly recycle plastic bottles?” The results were summarized in a 3-by-2 table of counts organized by grade level and yes/no response to the recycling question. The club performed a chi-square test for homogeneity across the three grade levels. Which of the following could be an appropriate null hypothesis used by the club?

1. H0: p1=p2=p3, where p1 is the proportion of the sample of sophomores that responded yes, p2 is the proportion of the sample of juniors that responded yes, and p3 is the proportion of the sample of seniors that responded yes.


2. H0: There is an association between grade level and whether or not a student regularly recycles plastic bottles.


3. H0: There is no difference in the distribution of regular recyclers across the three grade levels.