Statistics Chapter 2.1 Flashcards

Frequency Table and Classes

• A frequency table organizes data into categories (classes) and indicates the number of data points (frequency) in each category.
• Lower class limit identifies the smallest value in a class, e.g., for class 75-124, the lower limits are 75 and 125.
• Upper class limit identifies the highest value in a class, complementing the lower limits.

Class Boundaries

• Class boundaries differentiate between classes, ensuring no gaps; calculated as the average of consecutive lower and upper limits.
• For example, boundaries for classes 1-2, 3-4, and 5-6 are 0.5, 2.5, 4.5, and 6.5.
• Example class boundaries from the distribution 2-8, 9-15, 16-22 are 1.5, 8.5, 15.5, and 22.5.

Class Midpoints and Width

• Class midpoint is the average of the lower and upper limits, representing the center of a class.
• Class width is determined by the difference between the lower limits of consecutive classes.

Frequency Distribution Characteristics

• A typical frequency distribution contains between 5 to 20 classes.
• Appropriate class width is calculated as: (maximum data value - minimum data value) / (number of classes), rounded to the nearest whole number, preferably upward.

Types of Frequency Distributions

• Relative Frequency Distribution showcases each class's frequency as a percentage of the total, summing to 100%.
• Cumulative Frequency Distribution tracks the running total of frequencies, illustrating the accumulation of data over classes.