QMM240 Descriptive Statistics - I Statistical Methods for Business I - Lecture NotesPage: 1 Descriptive Statistics I Characteristic Interpretation Central tendency Data concentration? Typical or "middle values? Dispersion How variable? Unusual values? Shape Symmetric? Skewed? Flat? Peaked? Multimodal? Example: PERatios.xls I) Measures of Central Tendency: Can use dot plot, histogram and/or several statistics 1) Mean (or Average) The average of the sample nXXnii1The mean of the population NXNiix1Pro Con Familiar Sensitive to outliers Uses all the data
has intentionally blurred sections.
Sign up to view the full version.
QMM240 Descriptive Statistics - I Statistical Methods for Business I - Lecture NotesPage: 2 Obs #Value10.220.134.842.7525.6Average6.68Notice how the mean falls between data point 5 and the rest of the data. No values are very "close" to the mean. Example: JDPowers.xls Use =Average(data range)in Excel 1879398...1591641734639125.383737niixxnCharacteristics of the Mean 1()0niixxSum of differences of each data point from the mean is ALWAYS = 0 1()niixx= (42 –65) + (60 –65) + (70 –65) + (75 –65) + (78 –65) = (-23) + (-5) + (5) + (10) + (13) = -28 + 28 = 0 Mean is like a fulcrum. The data is balanced at the mean.