Statistics Week 2 Notes Section 2.1: Categorical Variables Descriptive Statistics­ Visualizing and explaining variable relationships Totalsample¿¿ Proportions= Number∈category ¿ Frequency table­ Shows the amount of cases in a category Bar plot­ The amount of cases is visually shown through the height of a Bar on a graph Difference in proportions­ A proportional difference seen in one category Section 2.2: One Quantitative Variable­ Shape and Center Dot plot­ 2 4 6 8 10 12 Bar plot­ 1 2 3 4 Note: Bars do NOT touch Histogram­ 1 2 3 4 5 Note: Bars DO touch Sample Size­ shown by the letter n ∑ of alldata Mean= , The mean shows the value averages Numberof datavalues Outlier­ A value that stands out from the rest of the data Resistant – A statistic that is unaffected by the outlier Ex: median Note: consider the possibility that the outlier could be a mistake Section 2.3: One Quantitative Variable­ Shape and Center Standard deviation­ For a numerical dataset, standard deviation measures the area that the data covers Σ(x−x)¯ Equation: s=√ n−1 Note: Standard deviation CAN’T BE NEGATIVE Ex: Which has a larger standard deviation A)11,21,30,42,50 Answer: B because the smallest and largest values B)5,16,32,50,62