Definition of Terms Individuals are the objects described
Definition of Terms Ø Ø Individuals – are the objects described by a set of data. Individuals may be people, but they may also be animals or things. Variable – a characteristic of an individual. A variable can take different values for different individuals. Ø Ø Categorical (Qualitative) variable – places an individual into one of several groups or categories. {Gender, Blood Type} Quantitative variable – takes numerical values for which arithmetic operations such as adding and averaging make sense. {Height, Income, Time, etc. }
Quantitative Variables Ø Discrete Variables – There is a gap between possible values. Ø Ø Ø Counts (no. of days, no. of people, etc. ) Age in years Continuous Variables – Variables that can take on values in an interval. Ø Survival time, amount of rain in a month, distance, etc.
Graphical Procedures Ø Categorical (Qualitative) Data Ø Ø Ø Bar Chart Pie Chart Quantitative Data Ø Ø Ø Histogram Stem-and-leaf plot (Stemplot) Dotplot Ø These plots describe the distribution of a variable.
Length of Stay 5 1 15 9 3 7 2 12 4 18 9 13 28 24 13 1 6 10 5 6 9
Fifth-grade IQ Scores 145 139 126 122 101 142 134 123 94 100 136 106 124 115 133 117 90 103 114 102 108 110 128 125 130 96 110 118 112 109 134 113 81 113 109 131 117 110 127 124 116 102 127 117 109 137 139 101 122 105 97 89 114 112 114 102 82 101
Distribution Ø The distribution of a variable tells us what values it takes and how often it takes these values Categorical Data Ø Ø Table or Bar Chart Quantitative Data Ø Ø Ø Frequency Table Histogram Stem-and-leaf plot
Describing a distribution Ø Skewness Ø Ø Ø Center/Spread No of peaks (modes) Ø Ø Symmetric Skewed to the right (positively skewed) Skewed to the left (negatively skewed) Unimodal, Bimodal, Multimodal. Outliers Ø Extreme values.
Homework Section 1. 2 : (pp. 24 -29) # 11, 15, 17, 23, 29.
- Slides: 8