# Think about how much time we spend using cell phones.

If somebody could please have it by tonight it would be much appreciated,

Student 1: Think about how much time we spend using cell phones. Have you ever wondered which cell phones would allow you to talk for the most time without having to recharge?

Student 2: Like which phones have the longest battery life?

Student 1: Exactly. I did some research and found that one cell phone manufacturer, ChatLong, claims that their phones average 18 hours of continuous talk time with a standard deviation of 2 hours.

Student 2: I found another cell manufacturer, Talk-a-Lot, that claims 20 hours of talk time and a standard deviation of 3 hours.

Clearly my company, Talk-a-Lot, is better. The talk time is longer.

Student 1: Their average talk time is better, but their standard deviation is bigger.

Student 1: I have an idea. Let’s each buy one of these phones and then try them out ourselves.

Student 2: You’re on!

Student 1: Then we’ll analyze our data as a sample using statistical methods to determine which company actually offers the best deal.

Student 2: Which phone company do you think is best?

1. Based on the info from the presentation:

Which company do you think makes the longest-lasting (and better) cell phone? Explain your thinking. (**1 point**)

2. Complete the table to summarize each student’s point of view: (**2 points**, 1 point for each)

**Student 1**

**Student 2**

3. a. Pick one of the two companies and sketch out a normal curve for it. Be sure to label it and use vertical lines to locate the mean and 1 standard deviation on either side of the mean. (**2 points**)

b. What is the range of values for each company to be within 1 standard deviation? (**2 points**)

c. What is the range for the 68-95-99.7 distribution? (**4 points**)

d. It may not make sense for the company’s data to be represented by a normal distribution. Look at the three graphs below represented by a curve and the x-axis. Which one is not possible? Why? (**1 point**)

4.The students each buy one cell phone and perform their own experiments to wear out the batteries.

Here are the data:

a. Based on their sample data, which of the cell phones is better? (**1 point**)

b. In order to properly compare the data, calculate the z-scores for each sample data point. (**2 points**)

c. Use a statistical calculator or a standard normal chart to find the percentile for each z-score you found in part b above. (**2 points**)

d. Now who do you think got the better cell phone (with longer battery life) and why? (**1 point**)

5. a. Is it problematic to decide that one company is better than another based solely on the students’ sample data? Explain. (**1 point**)

b. How would you improve the students’ experiment if you were going to conduct it yourself? (**1 point**)