Lecture on Graphing with Error Bars

Introduction

• Instructor expresses commitment to helping students, even outside of regular class hours.
• Reminder about students being absent due to a track meet.

Purpose of the Graphing Activity

• Focus on encouraging students to try and complete the graphing assignment without penalty for errors.
• Importance of attempting and showing work on graph paper.

Understanding Error Bars

• Definition: Error bars represent the standard error of the mean (SEM) values.
• Purpose: Helps in understanding the range of data values.
• Instructor recommends calculating and noting the range (e.g., 170±15 becomes 155 to 185) to prevent graphing errors.

Steps for Constructing the Graph

1. Preparation:

   • Use graph paper and write down calculations in advance.
   • Focus on labeling axes correctly.

2. Axes Labels:

   • X-axis for individual independent variables.
   • Y-axis for dependent variables like blood glucose level (unit: mg/dL).

3. Setting Range and Intervals:

   • Determine the range from the lowest (90) to the highest (200).
   • Include breaks in the graph if starting above zero.
   • Use consistent intervals; suggested by tens but could use fives based on space.

Plotting the Data

• Process:
  • Plot individual data points (1-8) and use error bars to reflect SEM.
  • Ensure proper spacing to avoid overlapping data points.

Statistical Significance

• Overlap in Error Bars:
  • Overlap indicates no statistically significant difference.
  • No overlap indicates a statistically significant difference.
• Examples:
  • Comparison between individuals with overlapping vs. non-overlapping error bars.

Tips for Clarity and Accuracy

• Draw dots clearly and make sure they are visible through the error bar lines.
• Ensure the error bars accurately reflect the SEM.
• Use a calculator for dealing with decimal SEM values.
• Understand the interpretation of SEM as it relates to the population range.

Conclusion

• Importance of revisiting concepts if absent from class.
• Encourage students to reach out with questions for clarity.