Standard deviation
The mean of a distribution of scores is the average.
Variance
Variance
You can't do this without knowing the distribution of scores.
They are said to be Normally distributed.
The distribution is skewed to the right.
If the distribution is Gaussian (or Normal) use z-scores. If it is Student's t, then use t-scores.
This simply means that if you plot a histogram of the scores it will be asymmetric.
If most the population has many high scores, the distribution is negatively skewed. If most have many low scores, it is positively skewed
z-scores are distributed according to the standard normal distribution. That is, with the parameters: mean 0 and variance 1.
The pattern is called a normal distribution, or a bell curve. It is characterized by symmetrical data points around the mean, with most scores clustering around the average and progressively fewer scores as you move away from the mean in either direction.
Add all of the scores you had (x) and then times the amount of tests (b) that you had by 100 (y), then use y-x= the overall score, now we need to find the average (a). use x÷b=a