In this activity, you’ll get 2 chances to guess at how long 30 seconds is, then look for an association between the 2 guesses of all students.

1. Work with a partner. Follow the instructions listed here to gather your data.
   • One of you will hold a stopwatch where the other person cannot see it.
   • The person holding the stopwatch says “go” and starts the timer.
   • The other person says “stop” when they think 30 seconds have passed.
   • The person holding the stopwatch will stop the timer then report and record the time to the nearest second.
   • The person holding the stopwatch will give a second chance, repeating the experiment.
   • After both times are recorded, switch roles.

2. Record the group data in this table. When you finish, a group member should give the data to the teacher.

   name	time 1	time 2

3. Look at your data. Comparing Time 1 to Time 2, do you think there is a positive association, a negative association, or no association? Discuss your thinking with your group.
4. What are some ways you could organize and represent the entire class's data?

5. Make a scatter plot of the entire class’s data and look for patterns. Identify any outliers and the type of any association you observe.

   

6. Draw 2 lines on your scatter plot: a vertical line and a horizontal line, each representing 30 seconds for one trial. Use the table for the class’s data to complete this two-way table.

   	time 2 < 30 sec	time 2 = 30 sec	time 2 > 30 sec	total
   time 1 < 30 sec
   time 1 = 30 sec
   time 1 > 30 sec
   total

7. Use the two-way table to decide whether there is an association between Time 1 and Time 2. Explain how you know.