Descriptive Stats

terms and definition

Measures of Central Tendency

These are statistical values that describe a set of scores by identifying the center point or typical score.

Mean

Is the arithmetic average of all scores.

Median

Is the middle score when the data are arranged in order.

Mode

Is the value that appears most frequently in the data set. 

Measures of Variability

These are statistics that describe the spread or dispersion of scores in a dataset.

Range

The difference between the highest and lowest values in dataset.

Variance

Measures the average squared deviation from the mean. It tells us how far scores spread out from the center.

Standard Deviation

The square root of variance. It tells us the average distance of scores from the mean in original units.

Spread

Refers to how far scores are from each other and from the average.

Consistency

Refers to how uniform or predictable the data is.

Skewness

Tells us about symmetry or asymmetry of a distribution.

Positive Skew

Most scores are low or average. A few extremely high scores pull the tail.

Negative Skew

Most scores are high or average. A few extremely low scores pull the tail

Kurtosis

Measures the height and sharpness of the peak in a distribution. It shows whether data are tightly clustered or spread out, especially in the tails.

Normal Distribution

A symmetrical, bell-shaped curve where most scores cluster around the mean, and fewer scores appear as you move away from it.

Skewed Distributions

A distribution where scores are not evenly distributed around the mean. One tail is longer than the other.

Outlier

A data point that is significantly different either much higher or much lower than the rest of the values in a data set.

Percentile Rank

Shows relative position in a distribution