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.
The sum of the differences between each score in a distribution and the mean of those scores is always zero because the mean is defined as the balance point of the distribution. When you subtract the mean from each score, the positive differences (scores above the mean) exactly cancel out the negative differences (scores below the mean). This property ensures that the total deviation from the mean is zero, reinforcing the concept that the mean represents the central tendency of the data.
z-scores are distributed according to the standard normal distribution. That is, with the parameters: mean 0 and variance 1.
Variance
Variance
Standard deviation
99.7% of scores fall within -3 and plus 3 standard deviations around the mean in a normal distribution.
The answer depends on the degrees of freedom (df). If the df > 1 then the mean is 0, and the standard deviation, for df > 2, is sqrt[df/(df - 2)].
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?
If the mean score is 100 and the standard deviation is 15, the distribution of scores is likely to follow a normal distribution, also known as a bell curve. In this distribution, approximately 68% of scores fall within one standard deviation of the mean (between 85 and 115), about 95% fall within two standard deviations (between 70 and 130), and about 99.7% fall within three standard deviations (between 55 and 145). This pattern indicates that most scores cluster around the mean, with fewer scores appearing as you move away from the center.
The median of a distribution of scores is the middle value when the scores are arranged in ascending or descending order. If there is an odd number of scores, the median is the middle score; if there is an even number, it is the average of the two middle scores. The median is a measure of central tendency that is less affected by outliers than the mean, making it a useful indicator of the typical score in a dataset.
skewed.