Frequency Table Construction

Constructing Frequency Tables

• Frequency refers to the number of times a particular outcome occurs in a dataset.
• A basic frequency table consists of two columns:
  • Categories of data (or ranges for numerical data).
  • Frequency for each category (number of occurrences).

Example 1: Eye Color

• An instructor records the eye color of 15 students.
• To create a frequency table, count the number of times each eye color appears:
  • Blue: 3
  • Brown: 7
  • Green: 2
  • Hazel: 2
  • Gray: 1
• Verify that the sum of frequencies equals the total number of items in the dataset.
  • $3 + 7 + 2 + 2 + 1 = 15$

Frequency for Qualitative and Quantitative Data

• For qualitative data (like eye color), list each possible category.
• For quantitative data (numerical), group data into numerical ranges (binning) instead of listing individual numbers.

Example 2: Exam Scores

• An instructor records exam scores for 15 students.
• Scores are grouped using five-point bins (ranges).
  • Five-point bins mean scores are grouped in increments of five (e.g., 60-64, 65-69).
• Frequency table:
  • 60-64: 1
  • 65-69: 2
  • 70-74: 1
  • 75-79: 5
  • 80-84: 3
  • 85-89: 2
  • 90-94: 1
• Verify that the sum of the frequencies equals the total number of items in the dataset.
  • $1 + 2 + 1 + 5 + 3 + 2 + 1 = 15$

Important Considerations

• When creating a frequency table, always double-check to make sure that count of each categories are accurate.
• If the sums of the frequencies does not equal to number of items in the dataset there may be values that were miscounted (either counted twice of missed).