How do the "Add" calculations work?
Below is a description, details, and some things to be aware of when using the three different Add calculations in Sentral Markbook.
Add
Description: Add values together
Accepts: One or more values
Notes:
Empty values will be counted as zero.
The result will be scaled if the total maximum marks of the values being added are different to the result's maximum mark
Standardised weighted add
Description: Convert values to z scores, weights z scores, and stretch results so that someone receiving 100% on every test would receive 100%, and someone receiving 0% on every test would receive 0%
Accepts: Two or more values. An amount of weightings equal to the number of values (these can be a ratio as well as a percentage)
Notes:
Any missing values for columns being added will cause this calculation to skip the student and give them an N/A.
The results will be scaled if the total maximum marks of the values being added are different to the result's maximum mark.
Other Things to look out for:
Standardised weighted add does not work with mark sets of 1 result. The process of converting marks to z-scores requires division by the standard deviation. A result set of 1 mark will always have a standard deviation of 0, and dividing by 0 is not mathematically possible. In this case, use Weighted Add.
Method:
The maximum mark for each column being weighted is converted to a z score, weighted, and added together (to find the maximum possible z score)
- The minimum mark for each column being weighted is converted to a z score, weighted, and added together (to find the minimum possible z score)
- Each student's marks are converted to a z score, weighted, and added together
- Each student's mark is stretched between 0 and 100 to reflect their position compared to the minimum and maximum z score possibilities
- Each student mark is scaled if applicable
Weighted add
Description: Convert values to a common denominator, weight, and add together. Scale to the new maximum mark
Accepts: Two or more values. An amount of weightings equal to the number of values (these can be a ratio as well as a percentage)
Notes: Any missing values for columns being added will cause this calculation to skip the student and give them an N/A.
Method:
- Divide each mark with it's maximum mark to get a percentage, multiply by the weight, and add together
- Convert each result to a percentage.
- Scale each mark if the new maximum mark is not 100
