2.2 Organizing, Displaying, and Communicating Scientific Data

From Raw Numbers to a Communicated Claim

Competency 002 treats data handling as a chain: collect it in an organized table, display it in the representation that fits the question, then communicate a conclusion that references the data. Exam items usually test one link in that chain — most often "which display should this student use?" or "what is wrong with this graph?" — so it pays to know the conventions precisely rather than approximately.

Designing the Data Table First

Students should build the table before collecting data, not after. A well-designed table has:

• The independent variable in the leftmost column, with its levels listed in order.
• The dependent variable in the columns to the right, with units in the column heading, not repeated in every cell.
• A column or set of columns for each trial, plus a computed mean.
• A descriptive title.

Building the trial columns in advance signals to students that repeated trials are expected, which is why table design and reliability are taught together.

Matching the Display to the Question

The distinction the exam presses hardest is bar versus line. Light color is a category with no in-between values, so bars are correct and a line would falsely imply that "red-and-a-half" exists. Time is continuous, so a line correctly implies that the temperature had a value between the recorded minutes.

Construction Conventions That Earn or Lose Credit

1. Axes. Independent variable on the x-axis; dependent variable on the y-axis. The memory hook is DRY MIX — Dependent, Responding, Y-axis; Manipulated, Independent, X-axis.
2. Labels and units. Every axis is labeled with the quantity and its unit: "Height (cm)", not "Height".
3. Scale. Intervals must be evenly spaced and should use most of the available grid. A scale that jumps 0, 5, 10, 50, 100 distorts the trend; an axis break must be marked with a zigzag symbol.
4. Title. Descriptive and specific: "Effect of Light Color on Bean Plant Height After 14 Days," not "Plant Graph."
5. Key. Required whenever two or more series share the same axes.
6. Line of best fit. For scatter data, draw a single straight or smooth line that passes near as many points as possible with roughly equal numbers above and below. Do not connect the points dot-to-dot; that claims each measurement is exact.

Maps, Imagery, and Other Representations

Topographic maps encode elevation as contour lines. Every point on a contour line has the same elevation; the contour interval is the vertical distance between adjacent lines. Closely spaced contours mean a steep slope; widely spaced contours mean gentle terrain. Closed loops with hachure marks pointing inward indicate a depression.

Satellite images and weather radar encode measured values as color, so the key must be read first: on a radar image, green through red is increasing precipitation intensity, not increasing temperature. False-color satellite imagery commonly renders healthy vegetation as bright red because it maps the near-infrared band to the red channel — a detail that reliably surprises students who assume image color equals real color.

Diagrams and models (a food web, the water cycle, a circuit schematic) communicate relationships rather than magnitudes and should include arrows whose direction is defined in a key.

Communicating the Conclusion

A scientific conclusion is not a restatement of the hypothesis. It has three parts, which map onto the Claim-Evidence-Reasoning structure used across Texas science classrooms:

• Claim — a direct answer to the investigative question ("Blue light produced greater bean plant height than red or green light").
• Evidence — specific data with units ("Mean height under blue light was 14.9 cm compared with 12.0 cm under red and 7.2 cm under green").
• Reasoning — the scientific principle that connects them ("Chlorophyll a and b absorb strongly in the blue and red bands and reflect green, so green light supplies the least usable energy for photosynthesis").

Oral presentations follow the same structure with a visual display, and both must state the limitations of the investigation — sample size, uncontrolled variables, instrument precision — rather than overclaiming. Teaching students to say "these data suggest" instead of "this proves" is part of the communication standard the framework describes.