2.5b Percentiles and Z-scores

Front

What is a percentile?

Back

A percentile is a measure used in statistics indicating the value below which a given percentage of observations in a group of observations falls.

Front

How do you calculate the percentile rank of a score?

Back

Percentile rank = (Number of values below the score / Total number of values) * 100.

Front

What does an 80th percentile score indicate?

Back

It indicates that the score is higher than 80% of the scores in the data set.

Front

What is a z-score?

Back

A z-score is a statistical measurement that describes a value's relationship to the mean of a group of values, expressed in terms of standard deviations.

Front

How is a positive z-score interpreted?

Back

A positive z-score indicates that the data value is greater than the mean of the data set.

Front

What does a z-score of zero signify?

Back

A z-score of zero indicates that the data value is equal to the mean of the data set.

Front

What is the formula for calculating a z-score?

Back

Front

If a student scored 21 points, the mean is 20, and the standard deviation is 3, what is the z-score?

Back

Front

What does a negative z-score indicate?

Back

A negative z-score indicates that the data value is less than the mean of the data set.

Front

What is the relationship between percentiles and z-scores?

Back

Percentiles provide a way to understand the relative standing of a score in a data set, while z-scores standardize scores across different distributions.