INTRODUCTION:

A graph is one of the tools used by scientists to interpret raw data. When we plot a graph, we do not connect the points, but instead we draw the best line of fit. Our data points from the raw data almost never fall in the straight line that they belong. This is because of experimental error. When we fit a line to our points, we draw the line the points should have been on. This is somewhat like an average, in that the line we draw is the best representation of our data points. The line may or may not go through any of our points, but it will have about equal points above and below it, which are about the same distance from the line. The correct answers are then any point along the line, and not our raw data points.
This takes practice and concentration to do well. In this lab we will use probability to practice finding a line on a graph.

MATERIALS:

6 dice
Cup
Ruler
graph paper

PROCEDURE:

1. You will be rolling 1 through 6 dice 25 times for each group. Start with one die and roll from the cup. Count the total number of evens (a 2, 4 or 6) in 25 rolls. Record the total number of evens on the DATA TABLE.

2. Now repeat step 1 with two dice, then 3, ect. until you have done six dice 25 rolls. Record the total number of evens for each group on the DATA TABLE. REMEMBER: You are looking for even numbers on each individual die. Don't add dots from one die to another.

DATA TABLE:
NUMBER OF DICE (x)	NUMBER OF EVENS PER 25 ROLLS (y)
1
2
3
4
5
6

GRAPHING:

3. On graph paper, plot your 6 sets of data points. The number of dice per group will be the horizontal or "x" axis. Number it out to 8 dice, even though you only used 6. The number of evens thrown per group will be the vertical or "y" axis. Try to use as much of the graph as possible.

4. Now, using a ruler, draw the best line of fit for your data points. Review the introduction so you are sure you know how to do this properly. Remember, for this graph x=0, y=0 is a point that your line will go through. Because if you rolled no dice, you would get no evens. Be sure to extend the line past where x=8.

CALCULATIONS:

5. According to your graph, how many even numbers would there have been for 8 dice rolled 25 times? Simply find where your line crosses the x=8 line, then go over to the "y" axis to find the value.

According to the graph, 8 dice rolled 25 times = _______ evens

6. Now calculate the mathematical value for 8 dice rolled 25 times. The probability of an even being rolled on a die, is 50%. REMEMBER: Percent must be converted to decimal form for multiplication.
The formula would then be:

8 X 25 X 0.5

Theoretical number of evens for 8 dice rolled 25 times. = _______ evens