Excel Norm S Dist Function and Finding Areas

Key Topics

• Excel Norm S Dist Command

  • Used to find the area to the left of a given z-score, equivalent to finding probability.

• Drawing Pictures

  • Important for visualizing problems.
  • Label the z-score; zero goes in the middle.

Finding Areas

• Types of Areas

  • Area to the left: Probability that z is less than a certain value.
  • Area to the right: Probability that z is greater than a certain value.

• Between Area

  • New focus: Finding the area between two z-scores.
  • Steps to Find Between Area:
    1. Draw the Picture
       • Label z-scores and the area you're interested in.
    2. Calculate Areas
       • Use Norm S Dist for each z-score to find area to the left.
    3. Subtract Areas
       • Subtract the smaller area (left of lower z-score) from the larger area (left of higher z-score) to find the between area.

Calculation Example

• Finding the Area to the Left of 2.18
  • = Norm S Dist(2.18) results in 0.9854.
• Finding the Area to the Left of 1.26
  • = Norm S Dist(1.26) results in 0.8962.
• Between Area Calculation
  • Subtract: 0.9854 - 0.8962 = 0.0892.

Common Errors

• Subtracting Z-scores
  • Incorrect to subtract z-scores directly to find between area.
  • Example: 2.18 - 1.26 results in a z-score of 0.92, irrelevant to finding probability.
  • Always subtract probability values, not z-scores.

Practical Application

• Using Computers
  • Practice with Excel to calculate and visualize.
  • Draw and label correctly.

Notable Points

• Decimal Precision
  • Many decimal values involved; ensure clarity.
  • Circle final answer for clarity.

Summary

• Use Norm S Dist to find areas related to z-scores in Excel.
• Subtract probabilities for between areas, not z-scores.
• Visual aids and distributions are crucial in understanding the concepts.