Calls claims that the mean length of all cell phone conversations in the United States is 3.25 minutes (3 minutes and 15 seconds). Assume that this is correct, and also assume that the standard deviation is 4.2 minutes.
a. Describe the shape of the distribution of the length of cell phone conversations in this population. Do you expect it to be approximately normally distributed, right-skewed, or left-skewed? Explain your reasoning.
b. Suppose that, using a phone company's records, we randomly sample 100 phone calls. We calculate the mean length from this sample and record the value. We repeat this thousands of times. What will be the (approximate) mean value of the distribution of these thousands of sample means?
c. Refer to part b. What will be the standard deviation of this distribution of thousands of sample means?

  • CreatedJuly 16, 2015
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