P.11 Describing Data

Purpose of Data Description

• Goal: To clearly and accurately communicate trends, patterns, and details observed in the results, often best done using a graph.
• Key Focus: Provide a detailed overview of the relationship between the independent and dependent variables, as shown on the graph, and support with specific data points.

Steps for Describing Data from a Graph

1. Identify the Overall Trend:

• Begin by describing the general relationship between the independent variable (x-axis) and the dependent variable (y-axis).
• Example: “As rennin concentration increases, the time to reach the end-point decreases, indicating that reaction rate increases with higher rennin concentration.”

1. Describe Gradient Changes:

• Note any changes in gradient (slope) on the graph.
• Example: “The gradient is steep at lower rennin concentrations, indicating a rapid increase in reaction rate, and becomes gradually less steep as concentration rises, showing a diminishing effect on reaction rate.”

1. Provide Specific Data Points:

• Quote key coordinates or data points directly from the graph, especially at points where there are notable changes in the relationship.
• Example: “At 0.2% rennin, the mean time to end-point is 68.0 s. At 1% rennin, the mean time decreases to 12.9 s.”

1. Assess Proportionality:

• Identify whether the relationship is proportional (linear) or non-linear (curved line).
• Example: “The graph forms a curve with a decreasing gradient, indicating that the relationship between rennin concentration and reaction rate is not proportional.”

Important Considerations When Describing Data

• Avoid Time-Based Language:
• Use terms that accurately describe the relationship on the graph. If the x-axis is not time, avoid phrases implying time such as “at first,” “quickly,” or “slower.”
• Correct Approach: Instead of “the gradient is steep at first,” say “the gradient is steep at lower concentrations and becomes shallower at higher concentrations.”
• Quote Data with Precision:
• Provide exact x and y values for key points to support your description.
• Quote values that help to highlight patterns, changes in gradient, or inflection points.

Example of Data Description

Using Figure P1.6 for reference:

“When no rennin was present, no reaction occurred, as indicated by an infinite time to reach the end-point (time = ∞). As rennin concentration increased, the mean time to reach the end-point decreased. For instance, at 0.2% rennin, the mean time was 68.0 seconds, whereas at 1% rennin, it was 12.9 seconds. The curve has a decreasing gradient, steepest at lower concentrations and flattening at higher concentrations. This non-linear trend shows that increases in rennin concentration have a greater effect on reaction rate at lower concentrations than at higher ones.”

Key Terms

Tips for Effective Data Description

• Use Accurate Vocabulary: Choose language that accurately describes the data on the graph without suggesting unintended meanings.
• Highlight Key Trends: Focus on major trends and patterns rather than minor fluctuations.
• Support with Data Points: Always back up your description with specific values or coordinates from the graph to provide evidence.