Student researchers at a private Midwestern college were interested in cell phone usage by students on campus and how it varied during different times of the day. They observed students walking around campus during the afternoon and recorded that 48 out of 232 students observed were using their phones in some fashion. During the evening, they observed 45 out of 115 students using their phones. We will assume these are representative samples from the population of all students at this college. Is the proportion of students on their phones during the afternoon different than in the evening? 

a. State the hypotheses either in words or using appropriate symbols. 

b. Calculate the difference in proportions (evening – day). 

c. Use the Multiple Proportions applet to calculate and report the standardized statistic and p-value. 

d. State your conclusion (with appropriate justification based on standardized statistic and on your p-value compared to the stated significance level) in the context of the research question. Be sure to also address the issues of causation and generalizability.