Measures of Center
Mean (average): add all values, divide by count. Affected by outliers.
Median: the middle value when data is sorted. For even-count sets, average the two middle values. Resistant to outliers.
Mode: the most frequently occurring value. A data set can have no mode, one mode, or multiple modes.
Range: max − min. Measures how spread out the data is.
Visualizing Data
A bar chart compares categories with rectangular bars. The height represents the value or frequency. Use bar charts for categorical data (colors, grades, types).
A line graph shows change over time — connect data points with lines to show trends.
A histogram is like a bar chart but for continuous data grouped into intervals (bins).