Describing Data with Numerical MeasuresGraphical methods may not always be sufficient for describing data.Numerical measures can be created for both populations populations and samples.samples.A parameter parameter is a numerical descriptive measure calculated for a populationpopulation.A statistic statistic is a numerical descriptive measure calculated for a samplesample.
Describing Central TendencyA measure along the horizontal axis of the data distribution that locates the center center of the distribution.
Three measuresArithmetic MeanMedianMode
Arithmetic Mean or AverageThe mean mean of a set of measurements is the sum of the measurements divided by the total number of measurements.nxxi∑=where n = number of measurementstsmeasurementheallofsum=∑ix
Example•The set: 2, 9, 1, 5, 6=∑=nxxi6.65335651192==++++If we were able to enumerate the whole population, the population meanpopulation meanwould be called μμ(the Greek letter “mu”).
•The median median of a set of measurements is the middle measurement when the