Chapter 1 Individuals objects described by data people animals Variable any characteristic of an individual o Categorical places an individual into one or more groups books songs gender model of car bar or pie graph o Quantitative number of pets owned number of books weight account balance numerical value usually unit of measurement attached age histogram 100 Distribution of variable tells us what values it takes hows often it uses variables Histograms o Appropriate for quantitative variables that take many values large data sets o One quantitative variable 1 Divide possible values into classes width 2 Count how many observations fall into each interval percentage 3 Draw picture representing distribution bar heights are equal to percent of observations in each interval o No space between bars Examining histograms pattern o Any graph of data look for overall pattern and for striking deviations from that o Symmetric skewed right skewed left o Skewed where the tail ends o Shape center x y spread smallest largest outliers sometimes none