Describing data
The vocabulary for summarizing a single variable: center, spread, shape, and the graphs that show them.
19 terms
Bimodal distributionA bimodal distribution has two distinct peaks, showing two values or ranges where observations cluster most heavily.DistributionA distribution describes the possible values a variable takes and how often each value or range of values occurs.Five-number summaryThe five-number summary reports a data set's minimum, first quartile, median, third quartile, and maximum.Interquartile range (IQR)The interquartile range (IQR) is the spread of the middle half of the data, equal to the third quartile minus the first quartile.MeanThe mean is the arithmetic average of a set of numbers, found by adding all the values and dividing by how many there are.MedianThe median is the middle value of an ordered data set, splitting it so that half the values fall below and half above.ModeThe mode is the value or category that appears most frequently in a data set.OutlierAn outlier is a data value that lies unusually far from the rest of the distribution.PercentileA percentile is a value at or below which a given percentage of the data falls, so about 90 percent of values lie at or below the 90th percentile.QuartileA quartile is one of three values that divide an ordered data set into four groups of roughly equal size.RangeThe range is a measure of spread equal to the difference between the largest and smallest values in a data set.Relative frequencyA relative frequency is the count in a category divided by the total number of observations, giving a proportion of the whole.Resistant statisticA resistant statistic is a numerical summary that changes little when a few extreme values or outliers are present.SkewnessSkewness describes the asymmetry of a distribution, meaning that one tail is longer or stretched further than the other.Standard deviationThe standard deviation measures the typical distance of data values from the mean, in the same units as the data.Symmetric distributionA symmetric distribution has a shape where the left and right sides are approximate mirror images about the center.Uniform distributionA uniform distribution is one in which every outcome or interval of equal size is equally likely, giving a flat shape.VarianceThe variance measures spread as the average of the squared distances between each value and the mean.Z-scoreA z-score tells how many standard deviations a value lies above or below the mean of its distribution.