Write an explanatory text that examines a complex idea with a thesis, headings, a table, extended definitions and precise vocabulary

Learning goal: Write informative/explanatory texts to examine and convey complex ideas, concepts and information clearly and accurately through the effective selection, organization and analysis of content. Establish a clear and thorough thesis to present information; introduce the topic and organize complex ideas so that important connections and distinctions are visible, using headings, graphics and multimedia when they aid comprehension; develop the topic with well-chosen facts, extended definitions, concrete details, quotations and examples suited to the audience; use varied transitions; use precise language and domain-specific vocabulary; keep a formal style and objective tone; and conclude by articulating implications or the significance of the topic.

The scenario this unit uses. Linden Ridge High School is invented, and so is every number attached to it. The school, which enrolls 1,140 students, is deciding whether to require students to lock their phones in magnetic pouches during class periods, unlocking them at lunch and at the end of the day. The simulated sources are these. Cost sheet: 1,140 pouches at 25 dollars each (28,500 dollars) plus six unlocking stations at 450 dollars each (2,700 dollars), a total of 31,200 dollars, to be paid from a one-time fund of 35,000 dollars. Pilot log: two ninth-grade English sections, 58 students in all, used pouches for six weeks; their two teachers counted phone-related redirections and recorded an average of 9 per 50-minute period in the three weeks before the pilot and 2 per period during it. Pilot quizzes: unit-quiz averages were 74 percent before the pilot and 79 percent during it, on different units. Student survey: 640 of the 1,140 students responded; 384 opposed the policy, 192 supported it and 64 were unsure. Parent letter: 41 families signed a letter asking how they would reach their children in an emergency. Oakmere report: a neighboring district, also invented, replaced 90 of its 750 pouches in the first year because of damage or loss. None of this describes a real school, and the evidence supports more than one reasonable position.

Explaining is not arguing. The argument lesson asked the board to do something. An explanatory text asks a reader to understand something. The difference is the writer's primary purpose, not the topic: explanations can take on disputed causes and interpretations, but they aim to build understanding rather than to win agreement to a claim. A useful test is whether a reader who disagrees about the policy could still learn from, and check, every sentence. The complex idea examined in this lesson is one that confuses adults as well as students: what a small before-and-after trial, such as the Linden Ridge pilot, can show and what it cannot. The idea is complex because it depends on several concepts that must be defined and then related to one another.

A clear and thorough thesis to present information. The thesis of an explanation presents the understanding the text will build, not a side, and it must be accurate for the information the text presents. "The pilot proves pouches work" fails as a thesis for these data: proves claims a cause, and a before-and-after count with no comparison group cannot establish one. (That one sentence does not reveal whether its text explains or argues; the purpose and development of the whole text decide the genre.) An accurate explanatory thesis takes two sentences here: "The pilot can show that the recorded counts changed in the classrooms it studied. Its design, a before-and-after count with no comparison group, cannot by itself show why they changed, and its size, two sections, cannot show whether they would change elsewhere; three concepts, a baseline, a confounding variable and replication, explain the difference." It is clear because a reader can restate what the text will show, and thorough because it names the distinction the text will draw and the concepts that will carry it.

Introduce the topic and organize to show connections and distinctions. Complex information needs an organization the reader can see. The model below introduces the topic with the question readers are already asking, then uses headings for its parts. Each heading marks a distinction (what changed versus why it changed) or a connection (how a baseline makes a comparison possible). Formatting such as headings lets a reader find a part again; a graphic such as a table lets a reader compare numbers side by side; multimedia such as a short recorded interview with the pilot teachers could let a reader hear how the counting was done. Include each only if it aids comprehension, and judge that by asking what it helps this audience see more easily than the prose does: a comparison, a scale, a location, a structure. Whether its facts also appear in the text is not the test. A table that only restates one number from the sentence beside it usually helps with none of these; a table that puts the pilot's measures, results and limits in rows is an aid, because the reader must compare them.

Develop the topic with well-chosen content. Development is where explanation becomes analysis. The standard names five kinds of content, and a good explanation mixes them: facts (the redirections fell from 9 to 2 per period), extended definitions (a paragraph that defines a confounding variable, gives its conditions and shows an example), concrete details (the counting took place in 50-minute English periods), quotations (the exact counting instruction the teachers followed, because its wording determines what was counted) and examples (a second, unrelated case that shows the same concept). Well-chosen means each item earns its place by helping the reader understand the thesis. Sufficient means there is enough of it for this audience to understand the whole thesis: enough facts, details, examples and explanation, connected to one another. Defining every concept the thesis names is one part of that, but a text can define every term and still leave an idea undeveloped. Appropriate to the audience's knowledge means you decide what the reader already knows: families do not know the term "baseline", so the text defines it; they do know what a quiz is, so the text does not.

An extended definition. A short definition gives a synonym. An extended definition gives the term's meaning, its conditions, an example and a non-example. A confounding variable is a factor, other than the one being studied, that differs between the conditions being compared and could itself cause the difference in the result. Condition: it must plausibly affect the outcome; a change in the classroom's paint color is not a confounding variable for quiz scores unless there is some reason it would affect them. Example: the pilot's quiz averages rose from 74 to 79 percent, but the quizzes covered different units, so unit difficulty changed at the same time as the pouches. Non-example: the two sections kept the same 58 students throughout, so a change in who was in the room cannot explain the drop. Two other limits are often confused with confounding. Observer bias is a measurement problem: the people recording the result may record it differently because of what they expect. A novelty effect is a change caused by the newness of a routine, which may fade; it limits how long a result can be expected to last.

Varied transitions that clarify relationships among complex ideas. Transitions in an explanation name the logical relation between ideas: in other words (restatement), for instance (example), by contrast (difference), as a result (consequence), more precisely (narrowing), in the same way (similarity), this matters because (significance). Varied means you choose the one that names the actual relation, not that you rotate words from a list. Transitions also link the major sections of the text and create cohesion: in the model below, More precisely opens the confounding-variable section by narrowing what the baseline section has just shown, and As a result in the replication section draws a consequence from the sample size it has just stated, so a reader moving from heading to heading still follows one explanation.

Precise language and domain-specific vocabulary to manage complexity. Every field has terms that compress an idea into a word. Here they include baseline (the measurement taken before a change), intervention (the change being tested), outcome measure (what is counted to judge the change), sample (the people studied), confounding variable, observer bias (a tendency for the people recording results to see what they expect) and replication (repeating a study and collecting new data to check whether the result is consistent; repeating it in other settings also tests how widely the result applies). Precise language also means exact verbs: the pilot recorded a drop; it did not prove a cause.

Formal style, objective tone, disciplinary norms. An explanation informs without selling. In a full text that reports data, a common norm is to state how the data were collected before stating what they show (a summary or abstract often gives the finding first), to give numbers with their units and to avoid words such as dramatic or huge that evaluate instead of report.

A conclusion that articulates implications. The conclusion follows from the explanation and tells the reader why the understanding matters: what it lets them do, or what question it leaves open.

Original model explanation — What a Six-Week Pilot Can and Cannot Show.

Introduction. When Linden Ridge's pilot reported that phone-related redirections fell from 9 to 2 per class period, some readers took the result as proof that pouches work, and others dismissed it as meaningless. Neither reading is accurate. The pilot can show that the recorded counts changed in the classrooms it studied. Its design, a before-and-after count with no comparison group, cannot by itself show why they changed, and its size, two sections, cannot show whether they would change elsewhere. Three concepts explain the difference: a baseline, a confounding variable and replication.

What was measured. The pilot's outcome measure was the number of redirections per 50-minute period. The two teachers followed a written rule: "Count one redirection each time you stop instruction to speak to a student about a phone." The wording matters. It counts interruptions to teaching, not how often students thought about their phones.

The baseline makes comparison possible. A baseline is the measurement taken before the intervention. For three weeks before the pouches arrived, the teachers counted an average of 9 redirections per period. In other words, the 2 per period recorded during the pilot means something only because there is a 9 to compare it with. Without the baseline, "2 per period" would be a number with no story.

Confounding variables and other limits on what the change can show. More precisely, the pilot shows that the recorded redirections fell, not why. That limit comes from the pilot's design, not its size: it compared the same classes before and after, with no comparison group that went without pouches during the same weeks. Anything else that differed between the baseline weeks and the pilot weeks could also explain the drop. For instance, the baseline came from the three weeks before the pilot and the pilot from the six weeks after, so classes may simply have settled into routines as the term went on; that difference in timing is a possible confounding variable. The quiz averages have a clearer one: the quizzes covered different units, so unit difficulty differed along with the pouches. Two further limits are not confounding but matter as much. The same two teachers counted before and during the pilot, and, having volunteered, they may have hoped it would help, so observer bias is possible: once they knew the pouches were in use, they may have counted borderline cases differently. And any new routine can change behavior for a few weeks simply because it is new, so the drop may not last. By contrast, some factors can be ruled out: the two sections kept the same 58 students throughout, so a change in enrollment cannot explain the drop.

Replication tests whether the result holds. Size sets a separate limit. The pilot studied 58 students in one subject and one grade. As a result, it cannot say what would happen with 1,140 students in every subject. Replication means repeating a study and collecting new data to see whether the result is consistent. Repeating the count in other classes, with staff who did not design the pilot, would do that and would also test whether the drop appears beyond the classrooms first studied.

Table 1. Three concepts in the pilot (concept — in the pilot — what it allows or limits)
Baseline — 9 redirections per period over 3 weeks — makes the drop to 2 measurable.
Confounding variable — later weeks of the term than the baseline; for quizzes, different units — prevents a firm claim about cause (observer bias and novelty are further limits).
Replication — not yet done beyond 58 students — needed before generalizing.

Conclusion. The recorded counts fell sharply in two classrooms, and that is worth knowing. This matters because the same three questions apply to any small trial a school, a company or a newspaper reports: what was the baseline, what else changed at the same time, and has anyone repeated it? A reader who asks them will neither dismiss the result nor treat it as proof.

Worked selection of content: A draft of the model included the sentence "The pouches are gray and close with a magnet that clicks." It is concrete and accurate in the scenario, but it helps the reader understand none of the three concepts the thesis names, so it is cut. The sentence that replaced it quotes the counting rule, because the rule's wording decides what the outcome measure measured. Well-chosen content is content the thesis needs.

Worked extended definition for a new audience: Term: observer bias. Short definition for experts: "systematic error introduced by the person recording results." Extended definition for families: "Observer bias is the tendency of the people recording a result to notice what they expect to see. It matters most when the thing being counted involves judgment. Deciding whether a moment counts as a phone redirection takes judgment: a student glancing at a pocket might or might not count. Two teachers who volunteered, and who may have hoped the pouches would help, might, without meaning to, count fewer borderline cases during the pilot." The extension adds a condition (judgment is involved), an application and a concrete case, and uses no term the audience does not know.

Worked transitions: Draft: "The pilot had a baseline. Also, the teachers volunteered. Also, the routine was new. Also, only 58 students took part." Every also hides the relation. Revision: "Because the pilot had a baseline, it can show that redirections fell. It cannot show why, however, since other explanations remain: the pilot weeks came later in the term than the baseline weeks, and the counters, who may have hoped the pouches would help, could have judged borderline cases differently. Moreover, with only 58 students, it cannot say whether the drop would occur school-wide." Because, however, since and moreover now name cause, contrast, explanation and addition.

Worked conclusion that states significance: Weak: "In conclusion, the pilot had good and bad parts." It restates nothing and implies nothing. Strong: "The pilot's recorded counts fell sharply in two classrooms; the same three questions about baseline, confounding variables and replication let any reader judge a small trial without dismissing it or treating it as proof." It follows from the three sections and tells the reader what the understanding is for.

Planning record: Choose a complex idea from another subject that you can explain to a ninth-grade audience in 600 words (for example, why a vaccine trial needs a comparison group, how a bill becomes a state law, or why the median can describe incomes better than the mean). Write an explanatory thesis that names the distinction you will draw and two or three concepts that carry it. List the headings you will use and state, for each, whether it marks a connection or a distinction. Draft one extended definition with a meaning, a condition, an example and a non-example. Decide whether a table, figure or short multimedia element would aid comprehension, and write one sentence justifying the choice.

Independent performance: Write a 600-800-word explanatory text. Success criteria: a clear and thorough thesis that presents information rather than a position; an introduction and at least three headed sections organized to show connections and distinctions; at least one graphic (table or figure) that the text refers to and that aids comparison; development that includes facts, at least one extended definition, a concrete detail, a quotation used because its wording matters, and an example; varied transitions that name the relationships between ideas; domain-specific vocabulary defined at first use; formal style and objective tone; and a conclusion that articulates the implications or significance of the topic. Attach a note naming one piece of content you cut and why.