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How is the R-score calculated?

• It is the sum of three components:

• The group used for R-score calculation may be a single class or several classes of the same course.
• At Marianopolis multiple-class groupings are used for every course in a given semester. This method of grouping provides a more balanced distribution of students of various academic strengths, generally resulting in more equitable R-scores than would result from grouping by individual classes.
• For the purposes of the R-score formula, group data (such as the course average, standard deviation and group strength) include only students whose course marks are 50% or more.
• The z-score is based on the student’s mark in the college course relative to the group average, and it also depends on the spread (standard deviation) of the course marks in the group. The individual z-score is positive for marks above the group average, and negative for marks below the average.
• The formula to compute an individual z-score is: 
  
               z-score = (course mark – group average) ÷ group standard deviation
  
  The group average used in the R-score formula is not a straight average, since it includes only marks above 50. The same applies to the standard deviation. In technical terms, the z-score measures the difference from the group average in units of standard deviation.

• The group strength index is based on the collective high school average of the students in the group. The group strength index is positive if the average of the combined high school records in the group is above 75, and negative if the group’s high school average is below 75. 
• The formula for computing the group strength index is: 
  
              group strength index = (group high school average – 75) ÷ 14
  
  The group average again excludes the high school marks of all students whose college course marks were below 50. The numbers 75 and 14 in this formula remain the same for all CEGEPs.

 
Example of an R-score calculation

• In a certain course the group consists of 150 students, among whom 145 obtained a course mark of 50 or higher.
• my mark in the course is 90;
• the average course mark for the 145 students with marks of 50 or higher is 80, with a standard deviation of 10;
• the z-score for my course mark is (90-80) ÷ 10 = 1.00
• the average incoming high school mark for these 145 students is 87, resulting in a group strength index of   (87-75) ÷ 14 = 0.86;
• my R-score for the course is  25 + 5 x 1.00 + 5 x 0.86 = 34.29

 
Note: The above formula is the basic one that applies in most cases, including the above example. Over the years a number of adjustments have been introduced, modifying certain extreme outcomes.

For instance, if in the above example the standard deviation is 12 with all the other figures the same, then the basic formula would yield an R-score of 33.45, while the adjusted one—which would be applied in this case—yields an R-score of 34.29 (the same as if the standard deviation were 10).

Example illustrating the effect of group strength 

• John is in a strong group whose collective high school average is 85. Peter is in a weak group whose collective high school average is 72.
• Suppose that their course marks are exactly equal to the average mark of their respective group (regardless of its value).
• John’s R-score will be 28.73, while Peter’s will be 23.93.  Peter’s course mark would have to go up by  8 to 10  points in order to match John’s R-score.

The group strength index was introduced into the R-score formula as a correction to the z-score (previously used by some universities), precisely for the benefit of colleges with a stronger student clientele. The result is that an average mark in a stronger group earns a higher R-score than an average mark in a weaker group.