Work out class grade curve instantly with clear inputs, formula shown and shareable results.
Curving methods differ in what they preserve. A linear shift adds the same marks to everyone and preserves the spread; the standard score method recentres the distribution and preserves relative standing; the square root method compresses the range and helps the lowest scores most.
Standard score method
Curved = Target mean + z x Class standard deviation
Linear shift
Curved = Raw score + (Target mean - Class mean)
Square root method
Curved = sqrt(Raw score) x 10
There is no universal answer. Linear shift is the most transparent; the square root method is the most generous to weak scores and the least defensible statistically.
Not under linear shift or the standard score method, since both are monotonic transformations. The square root method also preserves rank but compresses differences.