Statistics students were surveyed and two of the questions they were asked was what type of cellphone they use (Basic, iPhone®, Smart Phone that is not an iPhone) and how tall they are in inches to investigate a possible association between type of phone and student height. For the purposes of this exercise, we will consider this sample to be representative of all students at the school. The summary statistics are shown in the following table and the data are shown in the dotplots.

a. State, in words or symbols, the null and alternative hypotheses.
b. Using the summary statistics given, compute the MAD statistic.
c. A null distribution for this study is shown below. Using the MAD statistic you calculated in part (b) , will the p-value for this test be large or small? Explain.

d. Does it appear there is an association between type of cell phone used and height? If so, can you conclude the type of cellphone being used is causing the difference in sleep times? What is a possible confounding variable in this?

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Sample Standard deviation Type of phone Smart Phone Mean size 70.58 2.55 18 iPhone 66.90 4.65 61 Basic 15 67.10 2.93 .... Smart iPhone Basic 54 63 72 Height Cellphones *****