Percentiles Ranks are Descriptive Kin 175 Spring 2010 Emily H. Wughalter, Ed.D. Professor
What are norms? • Norms are predetermined performance standards. • Norms are good because the give everyone a chance to be excellent. • Norms should be changed about every three years.
Class Rank Norms This method is not very meaningful across groups, so use percentile ranks.
Median • The median is described as that score at which 50 percent of the group falls below or 50 percent falls above
Percentile Ranks • Percentile ranks describe the percent of the group that either falls below or above that number (e.g., 30th percentile means 30 percent of the group scored less than that number. • These are ways of describing our data to clients, students, parents.
What are some uses for Percentile Ranks? • Teachers and Fitness Trainers • Fitness reports • Student fitness tests • Reports to clients in a gym • Athletic trainers and physical therapists may make a comparison to a standard range of motion for an injured athlete. Use for goal setting.
Percentile Rank Norms • Norms are predetermined performance standards • Performance standards can be determined for a local, state, regional, national, or international norm
Normal curve graphic from http://en.wikipedia.org/wiki/Normal_distribution
Percentile rank scores tend the inflate the differences in the middle of the curve and deflate differences in the extremes of the curve due to the density of scores in the middle of the curve versus the sparseness of scores in the extremes. • Percentile rank scores are ordinal measures and therefore there is not a common unit of measurement between adjacent ranks. Normal curve graphic from http://en.wikipedia.org/wiki/Normal_distribution