The mean of a distribution of scores is the average.
z-scores are distributed according to the standard normal distribution. That is, with the parameters: mean 0 and variance 1.
Variance
99.7% of scores fall within -3 and plus 3 standard deviations around the mean in a normal distribution.
Scores on the SAT form a normal distribution with a mean of µ = 500 with σ = 100. What is the probability that a randomly selected college applicant will have a score greater than 640?
They are said to be Normally distributed.
The distribution is skewed to the right.
z-scores are distributed according to the standard normal distribution. That is, with the parameters: mean 0 and variance 1.
Variance
Standard deviation
Variance
99.7% of scores fall within -3 and plus 3 standard deviations around the mean in a normal distribution.
T-scores have a mean of 50 and a standard deviation of 10. These values are fixed and do not change regardless of the distribution of T-scores.
Scores on the SAT form a normal distribution with a mean of µ = 500 with σ = 100. What is the probability that a randomly selected college applicant will have a score greater than 640?
skewed.
You can't do this without knowing the distribution of scores.
If there are n scores and one score is changed by x then the mean changes by x/n.
They are said to be Normally distributed.