
Simulating Probability Situations Using Box Models
The interactive tool in this iMath investigation is
a "box model" to explore the relationship between
theoretical and experimental probabilities. A "box
model" is a statistical device that can be used to
simulate standard probability experiments such as flipping
a coin or rolling a die.
To use the "box model":
 To Enter Data: Click on the number pad to enter numbered tickets into
the box.
 To Randomly Draw Tickets: Click on the Start button to randomly draw
tickets from this box (with replacement) and view, in real time, the
experimental probability of drawing a given ticket.
 To Pause the Drawing: When you press the Pause button the "box
model" pauses drawing. You can then click on any bar in the bar
chart to display the current relative frequency.
 In pause mode, you are also able to scroll through the sample of the
numbers drawn thus far.
Sample Activity: Flipping a Coin
 Click on the 0 and the 1 to move them into the "box
model."
 Click the "Show Theoretical Probability"
checkbox to see the theoretical probability values displayed
on the bar chart.
 Read the bar chart to answer the following questions:
What is the theoretical probability for heads? For tails?
 Click on the Start button. (This begins a random draw,
with replacement).
 Click on the Start button to pause the drawing after
10 draws.
 After 10 draws, what is the experimental probability
of heads? Of tails? Why is this different from the theoretical
probability?
 Begin the drawing again by pressing Start. Pause after
20 draws.
 Is the experimental probability closer to the theoretical
probability than after 10 draws? Explain why more draws
affects the closeness of the two values.
 Predict the number of draws that would bring the values
"very" close to each other.
 Test your conjecture by beginning the drawing again
and pausing after you reach your predicted number of
draws. Repeat if necessary until you have gotten the
two values "very" close to each other.
 What hypothesis can you make at this point about the
number of draws it would take to insure that the experimental
and theoretical probabilities are equal?
The box model below allows you
to replicate the drawing of many numbers, and then investigate the distribution
of the sum of draws or average of draws. Try it. Describe and explain
any patterns you see.
References
