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Worksheet Grade 10 Art & Music

Ondine Creek Turbidity Chart: Grade 10 Honest Data-Design Worksheet

A grade 10 design worksheet where students build an honest bar chart from a fictional lab's turbidity readings, setting axis origin, scale, and reporting precision.

Objectives

  1. Students will set an honest axis origin and scale for a bar chart of test data.
  2. Students will convert readings into proportional bar heights on a grid.
  3. Students will report a reading and a mean to the precision of the measuring instrument.

Vocabulary

Turbidity
Turbidity is a measure of how cloudy or murky water looks because of tiny particles floating in it. Clear water has low turbidity, and muddy water has high turbidity.

Also: axis origin, false precision, scale

Teacher overview

Whether a bar chart reports its data honestly or distorts it comes down to a few design decisions. This worksheet gives students six monthly turbidity readings from the fictional Ondine Creek water lab and asks them to build a bar chart that reports the data honestly. Students choose where the axis starts, set a scale that turns each reading into a bar height on a grid, and decide how precisely to report a number given the instrument that produced it. The reference turbidity limit shown on the chart, 0.3 NTU, is the real drinking-water treatment standard.

Ondine Creek Turbidity Chart: Grade 10 Honest Data-Design Worksheet — Grade 10 Art & Music
Name: ____________________________ Date: ______________

Student Worksheet

The fictional Ondine Creek water lab measured turbidity, the cloudiness of the water, once a month. Turbidity is reported in NTU. The six readings are: January 0.12 NTU, February 0.18 NTU, March 0.24 NTU, April 0.30 NTU, May 0.21 NTU, and June 0.15 NTU. Show a reference limit of 0.3 NTU on the chart. Use these numbers.

  1. A bar chart of these readings should start its vertical axis at 0, not at 0.10. Explain how starting the axis at 0.10 would mislead a viewer.
  2. You draw the chart on grid paper where each grid square is 0.02 NTU tall. How many grid squares tall is the April bar at 0.30 NTU?
  3. How many grid squares tall is the January bar at 0.12 NTU?
  4. At the same scale, how many grid squares above the baseline should the 0.3 NTU reference line sit?
  5. Which month has the highest reading, and does that reading go above the 0.3 NTU reference limit?
  6. The lab's turbidimeter reads to the nearest 0.01 NTU. A student writes the April reading as "0.3000 NTU." Explain why that is false precision, and give the correctly reported value.
  7. Find the mean of the six readings, and report it to the nearest 0.01 NTU to match the instrument.
  8. Explain why coloring the six bars in six different bright colors would hurt this chart rather than help it.
  9. A newspaper can fit only 8 grid squares of chart height. Describe one honest way to fit the data in that space and one dishonest way you should avoid.
  10. Explain why a bar chart suits these six monthly readings better than a pie chart would.

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key
  1. Answer: Starting the axis at 0.10 cuts off the bottom of every bar, so small real differences look large. A 0.12 bar would look one-tenth as tall as the 0.30 bar, although 0.12 is actually 40 percent of 0.30, exaggerating the change.
  2. Answer: 15 squares. 0.30 divided by 0.02 equals 15 grid squares.
  3. Answer: 6 squares. 0.12 divided by 0.02 equals 6 grid squares.
  4. Answer: 15 squares. The 0.3 NTU line sits at 0.30 divided by 0.02, or 15 grid squares above the baseline, level with the April bar.
  5. Answer: April. April's 0.30 NTU is the highest reading, and it equals the 0.3 NTU limit rather than going above it.
  6. Answer: 0.30 NTU. Writing "0.3000 NTU" claims accuracy to four decimal places, but the instrument reads only to the nearest 0.01, so the honest report keeps two decimal places: 0.30 NTU.
  7. Answer: 0.20 NTU. The six readings sum to 1.20, and 1.20 divided by 6 equals 0.20 NTU, reported to the nearest 0.01.
  8. Answer: Six bright colors imply the months belong to different categories and pull the eye to color instead of height. One consistent color keeps attention on the bar heights, which carry the data.
  9. Answer: An honest fix keeps the axis at 0 and uses a smaller scale, such as 0.04 NTU per square, so all data still fits. A dishonest fix would raise the origin above 0 to shrink the bars into the space.
  10. Answer: A bar chart compares separate monthly values, which is what these readings are. A pie chart shows parts of one whole, and monthly turbidity readings are not shares of a total, so a pie would misrepresent them.

Differentiation

Support

Provide grid paper with the vertical axis already labeled from 0 to 0.36 in steps of 0.02, and work item 2 aloud as a model before students continue. Give the six readings on a reference strip so students do not recopy them.

Extension

Ask students to redraw the fictional lab's chart at a scale of 0.04 NTU per square, state the new height of the April bar, and explain in writing how changing the scale changes the chart's appearance without changing what the data honestly shows.

ELL supports

Provide a bilingual glossary card for "turbidity," "axis," "scale," and "precision," each with a small image. Allow the explanation items to be answered with short phrases or an annotated sketch of the chart rather than full paragraphs.