D2.1 Use fractions, decimals, and percents to express the probability of events happening, represent this probability on a probability line, and use it to make predictions and informed decisions.
Knowledge: Probability Line
As students understand that it is possible to use a fraction to describe the probability of an outcome, they can place that outcome more accurately on a probability line.
image The probability line shows a bar starting from white and gradually turning dark blue. The top of the bar is graduated as follows: Impossible, one in four possibility, one in two possibility, three in four possibility and certain. The bottom of the bar is graduated as follows: zero, zero percent. One quarter, zero point five, 25 percent. One half, zero point five, 50 percent. Three quarters, zero point 75, 75 percent. One, one hundred percent. In the center of the bar it says "Probable," with two arrows pointing to the extremes of the bar.
Source: translated from Guide d’enseignement efficace des mathématiques, de la 4e à la 6e année, Traitement des données et probabilité, p. 141-142.
The numerical values of the probability of events range from 0 to 1, and its percents range from 0% to 100%.
Fractions and decimal numbers can be used to express the probability of events in the 0 to 1 continuum.
Example
Probability line showing the probability of outcomes for an experiment involving rolling two six-sided dice.
image A rectangle is separated into two parts. On the left part, which is yellow, it says "Unlikely". On the far left, it says "Impossible Event", zero percent, 0. A little further to the right, a black dot says 17 percent, the total of 4 and less. In the middle of the yellow rectangle, it says 25 percent. On the line that separates the yellow side from the light purple side, it says 50 percent, equiprobable. In the light purple part, it is written "Very probable". In the center of the light purple area, it says 75 percent. A little further to the right, a black dot indicates 83 percent, total of 5 and more. On the far left, it says 100%, certain event.
Source: The Ontario Curriculum. Mathematics, Grades 1-8 Ontario Ministry of Education, 2020.