# ISDS 361B Ch. 4

 What r the 3 different measures to describe the center of a set of data? MeanMedianMode Mean? It is the average. Median? Central location. gives you the middle where 50% of the numbers lie on each side.*When there is an even # of observations, the median is determined by averaging the 2 observations in the middle. Mode? the observation with the greatest frequency Why is Mode not a good measure to use? In small samples not a good measure to useit may not be unique How do you compute mean, median and mode on excel using one button? Data Anaylsis --> Descriptive Statistics (then input the range of numbers) --> Summary statistics. Which central measure is best? Mean is used most often, but median could be better because it is not sensitive to extreme values. When to compute Mean? Interval datau want to describe a single set of data When to compute Median? Interval or Ordinal data (w/extreme observations)Describe a single set of data Ordinal data - categorized with meaning Range Largest observation - Smallest observation pg. 106 What are the measures of variability for interval data only? RangeVarianceStandard DeviationCoefficient of Variation Is Variance a good way to explain a set of data? What could it tell us when compared to another set of data? No, cuz it only gives us a rough idea of the variation in the data. Comparing to another set of data it could tell us if the 1st set of data has more variation than the 2nd set. Variance interpretations are problematic cuz we squared the deviations to get the mean. How do you fix this problem? you calc the standard deviation. Units associated with SD is the unit of the original data set. pg. 110 How do U interpret Standard Deviation? Empirical Rule - Bell ShapeChebysheff's Theorem - all shapes Empirical Rule Ex: histogram is bell shaped. mean and SD are 10% and 8%. Interpret 68% fall in between 1 SD, so 18% and 2%95% fall in between 2 SD, so 26% and -6%99.7% fall in between 3 SD Chebysheff's Theorem provides lower bounds75% lie between 2 SD88.9% lie between 3 SD Coefficient of Variation Indicates whether the SD (variation) is large or small compared to the number of observations. SD / by their mean How do you word the Chef theorem? At least 75% of the numbers lie betweenAt least 88.9% of the numbers lie between Authortv ID39481 Card SetISDS 361B Ch. 4 DescriptionTechniques Updated2010-10-04T03:21:19Z Show Answers