Average test scores with different weights.
A weighted average multiplies every score by its weight, sums the products and divides by the total weight — so a test carrying half the marks influences the result five times as much as one carrying a tenth. The weights do not have to add to 100; the division by their sum normalises them automatically. Showing the unweighted mean alongside makes the weighting effect explicit: when the difference is positive, the heavier tests are the ones you did better on.
Weighted average of test scores
Weighted average = (s1 x w1 + s2 x w2 + s3 x w3) / (w1 + w2 + w3)
No. The formula divides by the sum of the weights, so 2/3/5 gives exactly the same answer as 20/30/50. Only the ratios matter.
Enter your expected score for it. The weighted average then reads as a projection, and you can vary that one score to see how much the outstanding test can still move the result.
Because your weaker scores carry the heavier weights. The effect figure quantifies exactly that gap — it is the penalty the weighting scheme imposes on your particular pattern of results.