Week 11 — Biking Is Booming? Checking the Numbers in a Program Newsletter — Traditional alternative (no AI)

Instructors: publish this instead of the adaptive version if you prefer, and unpublish or delete the adaptive one.

Assignment 10 of the term — find the conclusion a newsletter's numbers are offered to support, turn a change in a share into percentage points and a percent change, give a change in risk both ways with its base named, count the people behind a screening claim, read a bar chart's axis, and explain to someone new what the numbers really show.

This week you learned to find the conclusion a number is offered to support, to report a change between two percents in percentage points and as a percent change, to give every change in risk both ways with its base named, to count the people behind a screening claim, and to read a graph's axis before its shape. In this assignment you work four short problems on one illustrative newsletter item, interpret each one, find its premises and conclusion as Week 1 taught you, and explain to someone who has never studied critical thinking what the numbers really show. This week's lecture tutorial, quiz, discussion, and Argument Workshop practise the same ideas from other angles.

The task

Your text is an illustrative newsletter item from a city's bike-share program, with no real city, program, company, or rider behind it: "Biking is booming! The share of downtown commuters who bike to work rose from 12 percent last year to 21 percent this year, up 75 percent. Our new protected lanes cut riders' risk of a commuting injury by a quarter. Our smart locks are 90 percent accurate, so when a lock sounds an alarm, the bike is almost surely being stolen. And our bar chart of rider satisfaction shows the bike line's 78 towering over the bus line's 60. So the city council should double the bike-share budget next year."

Work these four problems, showing your arithmetic and quoting the sentences you use:

1. The share of downtown commuters who bike to work rose from 12 percent last year to 21 percent this year. By how many percentage points did the share rise?
2. The program's records show that riders' risk of a commuting injury fell from 12 in 1,000 riders to 9 in 1,000 riders. By what percent did the risk fall in relative terms?
3. In one month the program's locks guarded 2,000 bikes. One bike in 100 was tampered with, the locks sounded an alarm on 18 of the tampered bikes, and they also sounded a false alarm on 5 percent of the bikes no one touched. How many alarms sounded in all?
4. The newsletter's bar chart shows a rider rating of 78 for the bike line and 60 for the bus line, on a vertical axis that starts at 57. By what percent is the bike line's rating higher than the bus line's?

Beside each answer, add one brief interpretation:

• Problem 1: name the conclusion the newsletter's numbers are offered to support and two of the premises offered for it, say whether "up 75 percent" is a change in percentage points or a percent change, and rewrite that sentence so it reports both.
• Problem 2: give the same change as an absolute change with its base named, say which kind of change the newsletter reported and which it left out, and explain why a reader needs both.
• Problem 3: say how many of the alarms came from tampered bikes, name the mistake in "the bike is almost surely being stolen", and explain why a lock that catches most tampered bikes still sounds mostly false alarms.
• Problem 4: say how tall each bar is drawn above the axis start and how many times taller the bike bar looks, name the graph trick, and then write the message to the neighbor described below.

Explain it to a non-expert

A neighbor who sits on a neighborhood advisory board reads the newsletter and asks, "Biking is up 75 percent and the locks are 90 percent accurate, so the program is a big success and an alarm means a theft, right?" Write a 3–5 sentence message that explains in everyday words what the biking numbers really show, reports the rise in the biking share both in percentage points and as a percent change, says how many of the month's alarms came from tampered bikes, and names one limit: the newsletter's numbers, read correctly, still do not settle whether the budget should double. Explain any technical term in everyday words. More than one good answer is possible.

For a different, ungraded example, imagine a café sign that says "Our loyalty-app sign-ups doubled this year!" after sign-ups went from 40 members to 80. Model answer: "Doubled is true, but it means 40 more people joined, which is a small group for a busy café. The sign gives the growth and leaves out the size, so it sounds bigger than it is. Before deciding the app is a hit, I would want to know how many customers the café serves in all. The number is a reason to look closer, not proof of success."

Use that pattern for the neighbor, with your own wording and evidence.

Show your arithmetic, write each term out in full, and quote the sentences you use. A reader should be able to reproduce every number you report, and find every quoted sentence in the newsletter, without guessing which values, steps, or sentences you used.

Deliverables

Submit a single report containing:

• the four answers, each with the arithmetic shown and the brief interpretation the task names for that problem;
• your message to the neighbor, explaining what the biking numbers really show, reporting the rise in the biking share both ways and how many alarms came from tampered bikes, and naming one limit; and
• a one-line restatement of the values you used (the two biking shares, the two injury risks, the month's lock counts, and the two ratings with the axis start), so your answers are reproducible.

Keep it to roughly one page. Clear and correct beats long.

Choose how you show it. Present your report as written text, or as a recorded audio or video explanation of about three minutes with a transcript, or as a labelled sketch that shows the two bars drawn from the axis start beside the same two bars drawn from zero, with a short note that says each verdict in words. Every form is graded by the same scoring criteria. Submit in any accessible file type or as a link; a recorded response may be submitted as audio or video with a transcript, or as text.

How you'll be graded

The full analytic rubric is attached to this assignment in Canvas.

Academic integrity and AI use

This version is designed to be completed without AI: do the computations, the interpretations, and the writing yourself, without a chatbot or other AI tool. Quote the newsletter only as it is printed here, word for word. Submitting AI-generated work as your own, or copying another student's work, is an integrity violation under the course policy.

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