祝融说。

Why the Achievements in the Cabinet All Look Smooth

Gu Ning reopened the original stack of eight display cards. They had not become false material through the checks of the preceding chapters: the repair station genuinely completed these jobs, and the cards retain the achievements. But she could now ask a further layer of the question—why did objects of this kind enter the cabinet, and why are other objects not in this stack?

Chapter 3 first identified the acquisition entrance for material, Chapter 4 established a comparable set, and Part Two examined conditions and evidence. Part Three asks a further question about the selection mechanism: if the chance of material entering is related to the target outcome, how does the proportion of visible objects change, and which inference about the whole thereby loses support?

This chapter continues the thought experiment of the fictional Chengwan repair station. The registration of sixteen items, the display of eight cards, the twelve original records that can be found, and the four still missing all remain, and R17 still lacks complete confirmation. The eight displayed items and the eight comparable items must not be treated as the same group merely because the counts are equal.

That material is genuine and what the material represents are two successive judgments. The former being established does not automatically carry the latter; pointing out that the latter is limited is not a denial of the work done in the past. Selection can be part of a legitimate use; the error occurs when the range compressed out by that use is expanded into the whole question.

Re-examining the Display Rules Rather Than Guessing Hidden Motives

At 2:20 p.m. on Thursday, Ye Cheng re-examined the production instructions for the display cards. This chapter explicitly adds a setting: this stack of cards was produced to introduce completed achievements, and the production conditions included repair completion, the availability of a displayable photo, and obtaining the corresponding display permission. It was not a scheme of making one card for every registered request.

These several conditions determine that certain objects did not enter. Requests that were not completed fail the achievement entrance; requests completed but without a displayable photo or permission may also fail. Hence the absence of a display card does not mean the absence of completion, and having a card does not mean confirmation within the first-version window as Gu Ning defined it.

Gu Ning does not infer from this production scheme that anyone deliberately concealed failures. An introduction to achievements may reasonably select photos, and may respect display permissions; it simply did not take on the task of being a ledger of outcomes for all requests. A legitimate use does not guarantee fitness for the current prediction, and a limited use does not imply malicious content.

This chapter has not supplied a complete mapping between the eight cards and specific R numbers, so none of them can be forcibly assigned to the original five confirmations. What has been newly obtained is the display rule, not the full outcome of every request, nor the reason the four original records are missing.

Giving "Being Visible" a Condition of Its Own

Let S denote that an object was selected by the current entrance and became visible material this time. When the original target is denoted A, the proportion of A among the visible material corresponds to the range conditional on S; the proportion of A in the original target population is not directly given under this display condition.

Chapter 7 already showed that conditioning changes the denominator. What is added here is that S is not a natural property of the task object but the process by which material comes before one's eyes. If Gu Ning is unaware of S, she still counts within a restricted range, yet may report the result as if it described an unrestricted population.

S can also involve multiple thresholds. First completion, then photographability, then permission to display, then being placed where it is easiest to find—each threshold can change which objects are actually visible. At which stage each threshold operates requires material; it cannot be filled in with a made-up story just because everything looks smooth in the end.

On the additional representativeness assumptions needed to use non-probability samples for population inference, see the sample design discussion in Statistics Canada's 2009 Quality Guidelines. This chapter does not treat the achievement cards as formal survey sampling; it borrows the point only to make one thing explicit: ease of acquisition is not proof of population correspondence.

How a Hypothetical Table Displays the Effect of Selection

To compute the effect clearly, the following sets up a separate comparison of twenty items; all figures are hypothetical and are not added to Chengwan's R01–R16 registration. Suppose all twenty items can be adjudicated against the same target A, ten succeeding and ten failing, a population proportion of one half.

Suppose further that a material entrance admits six of the ten successes and two of the ten failures; every admitted item's outcome is recorded faithfully, with no miswriting and no duplication. Among the eight visible items, six succeed—a proportion of three quarters.

Three quarters is not miscalculated; it answers the proportion of outcomes among the eight selected items. One half is not miscalculated either; it answers the proportion over all twenty items. The two differ without any single item of material lying—only through the admission process treating the two classes in different proportions.

In this table, S admits three fifths of the A group and one fifth of the non-A group. The entrance makes A objects occupy more of the visible range, and so the visible proportion exceeds the original proportion. The mechanism is displayed here with explicit numbers; it is not claimed that the actual strength of Chengwan's selection has been shown to equal these two figures.

More Admitted Items Do Not Mean More Population Support

If another, larger hypothetical set multiplies each class tenfold—of the original two hundred items, one hundred succeed and one hundred fail, and the entrance admits sixty successes and twenty failures—the visible eighty items still show three quarters, and the population still one half.

The visible sample grew from eight items to eighty, yet the selection mechanism was not eliminated merely because the count grew. A larger count may let one see the proportion within the selected range more stably, but that number cannot be used in place of the unselected population; increasing quantity and the coverage mechanism are two different problems.

Nor can one say in reverse that large samples are always useless. Quantity has a real role in many estimates and tests, and its specific role depends on design and model. This comparison rules out only one erroneous inference: under the same differential admission proportions, increasing the visible count by itself will not automatically turn the range conditional on S into the original population.

For Gu Ning, the first question is therefore not whether eight cards are enough, but why the eight entered. If the achievement cabinet is merely expanded into a bigger achievement cabinet, the completion entrance remains, and so does the judgment range that lacks incomplete objects.

Balancing the Counts Also Cannot Replace a Selection Rationale

Consider another hypothetical comparison: if among the twenty items there are still ten A and ten non-A, and the entrance takes four from each side, then A makes up one half of the eight visible items. This sample proportion coincides with the population, and can be reported faithfully on the basis of this table.

But one cannot say, merely because the admitted counts are balanced on the two sides, that the selection process is problem-free at all times. Here it is known in advance that each side originally had ten items; if the two classes had different shares in the original population and four were taken from each by design, the equal-weighted visible proportion would still be one half and might no longer correspond to the population.

Chapter 7 explained that reconnecting groups to the population requires group shares; this chapter puts that requirement back into the selection process. Collecting equal numbers for ease of comparison can serve particular questions; to report population proportions, one must still state how large each group's share is in the target range and how the selection corresponds to it.

One therefore cannot casually add a few failure cases to make the table look balanced on both sides, and then declare the bias corrected. How the additions were selected, what part they represent, and whether the gap in original records has changed—all require explanation. A more symmetric table is not a better-grounded model.

The Selection Condition May Hide in Search Convenience

When Gu Ning searched for original records, objects on the display cards were usually easier to find documents for, because achievements had been centrally organized. Even if she did not filter by possession of a card, if she only worked through the most easily found batch, convenience could re-enter as a condition of S.

This does not mean that always searching the easy objects first necessarily produces bias of a known direction. If convenience has no important correspondence with the current target, the effect may differ; if it is related, it must be stated. But whether a direction exists, and how large it is, cannot be decided solely by the organizer's intuition.

One can record which cabinet was searched first, which objects required additional searching, and why the search stopped temporarily. Preserving the process is not a way of imputing values for all outcomes; it leaves real material for later examination of the selection relation. If easy-first, hard-later searching eventually covers the same defined range, the initial convenience and the final inclusion may again differ.

Chapter 3 yielded an acquisition account; this chapter takes one more step: how acquisition order and stopping rules may affect the analyzed set. What Gu Ning should preserve is the conditions for entering the final count, not merely which documents first came to hand.

Choosing Comparison Objects After the Outcome Is Known

If Gu Ning wants to find requests similar to R17, filtering by starting version, window, and available fields can be justified by the question. But if, after seeing the outcomes, she calls similar only those objects that matched her original expectation, the comparison class is being shaped in reverse by the results.

The same word can cover different acts of selection. Whether "similar" means similar in task, stage, or material scope, or merely that all later received approval, must be made explicit in the account. A group name that sounds neutral must not be used to legitimize screening by outcome.

For R01–R08 this book already has version and window correspondence, with five successes and three failures both retained; the three failures were not deleted to produce a nicer frequency. This chapter does not claim that this group fully represents the future on all important conditions; it states only that the current eight-item denominator was not constructed directly by positive outcome.

Selection rules may be revised later, but the new rationale, the time of acquisition, and the affected objects must be written down. If new material shows that a stage does not correspond, reclassification is permissible; if only the outcome is unwelcome, objects may not be removed from the record without a stated reason.

A Genuinely Filtered Range Can Have Uses

If the question really is which completed, display-permitted achievements exist, the eight cards are directly relevant material. If one studies how such achievements are presented, that can be done within the range of S, without first finding the full registered outcomes for every purpose.

The question is whether S continues to be omitted after the use changes. Using these achievements to introduce to readers the work that has been done, and using them to predict the original-window confirmation rate of newly registered requests, are different tasks. Material can be legitimately reused, but reuse requires re-examining the conditional interface.

Gu Ning can preserve two products: the achievement display retains the facts of what was completed, and the prediction ledger is organized separately by request and window. The two help locate each other and do not replace each other's denominators. Pointing out the inadequacy for prediction does not demand destroying the achievement introduction.

This division of labor also avoids another rigidity: refusing all selected material for fear of bias. All limited observation has an entrance; what is needed is an account of how the entrance connects to the use, not the pursuit of a panorama with no conditions whatsoever.

Missing Relations Cannot Be Inferred Backward from Display Relations

R13–R16 lack original records for now, and their causes and outcomes remain unknown. The display rule required completion and permission, which does not prove that these four were incomplete, or lacked permission, or were deliberately hidden. The two entrances have different mechanisms; seeing one kind of selection does not license supplying causes for the other.

That the eight cards and the twelve original records overlap also does not mean the missing four items' window adjudications can be completed through the cards. The cards may provide achievement facts, yet still lack the original first version, the starting point, or the deadline communication; partial completion of material does not make all fields complete.

If correspondence is later obtained, one may note which gap has shrunk. If it is still not obtained, the registration and unknown status are retained, and the missing set must not be lumped together as negative samples. The next chapter will unfold unobserved outcomes and survivor stories; here the distinctions between mechanisms are protected first.

An account of selection should be written in three layers: known rules, possible relations, and unknown relations. Knowing how the display entrance works does not guarantee that the size of the population-level outcome shift is known; proposing that material acquisition may be related does not mean Gu Ning has proven that the four items belong to some outcome.

What Support Does Reweighting Require?

In the hypothetical twenty-item table above, if it is fully known that ten are A and ten are non-A, the population proportion of one half can be given directly; there is no need to pretend the population was discovered from the eight visible items alone. Knowing the selected proportions also allows one to check how selection changed the shares—but those proportions come from an additional complete setting.

If reality offers only the eight visible items of unknown provenance, with neither original class counts nor each class's admission chances, one cannot directly follow the hypothetical table and inflate six and two into ten and ten. Weights are not a matter of speaking for the unseen by intuition; they require a source, a model, and applicable assumptions.

Additional material may be used to check the object range, and explicit hypothetical scenarios may be constructed, stating which results change with the assumptions. A correction formula must not be treated as already possessing the facts of unseen objects; still less may all unseen objects be given identical weights without stated grounds.

This chapter has not computed sampling weights, error intervals, or population confirmation rates for the Chengwan achievement cards. The selection mechanism has not yet been fully quantified; the most accurate current action is to restrict the use and preserve an interface for further checking.

Selection Can Also Occur in Retelling and Conclusions

Even when the original records have been fully acquired, if the handover person retells only the smoothest items, a new S may form before the receiver. Selection does not occur only at initial collection; it can appear in summaries, recommendations, displays, and final reports.

Consider a retelling comparison: if the same fourfold table is presented by telling only the three items that are both B and A, without the objects that are B and non-A, or non-B yet A, the original table is not wrong, but the retelling narrows the currently visible range. Chapter 8 protected different denominators; this chapter adds the question of why the retelling let only certain cells appear.

One may point to the full table alongside the conclusion, stating the purpose of the examples and the correspondences not narrated. Concise communication permits selection and does not require every sentence to carry all the data; but when readers need to return to the full range, there should be an entrance, and the summary must not itself serve as the whole of the evidence.

If later consensus preserves only the smooth story, selection becomes hard to recognize through repeated transmission. Chapter 18 will unfold the effect of consensus on visible material; here an interface is left: transmission, too, has conditions of admission.

Screening Out Non-Corresponding Objects Differs from Deleting Counterexamples

R09–R12 have original records, yet did not directly enter the original eight-item comparison because of stage or window differences. Such scope restriction can serve the current question; it should not, merely because it is also called selection, be merged into the same error as deleting the three failures.

The key is whether the rationale corresponds to the question, can be traced back to material, and is applied equally to positive and non-held outcomes. If an item simply cannot correspond to the original first-version window, forcing it in may create another kind of error of meaning; if it can correspond and was removed only because the outcome was unfavorable, then the denominator has been screened by outcome.

Gu Ning can leave a reason for each item not directly compared for now, preserving the original registration for other uses. Exclusion does not make the actual object vanish, and not currently applicable does not mean failure. This makes scope selection open to objection: if new material proves the original stage in fact corresponds, the item is rechecked rather than permanently rejected for having been excluded earlier.

More material is not always better, and not every screening biases judgment in the same way. Whether a selection is appropriate must be discussed together with the target and its support; this boundary keeps this chapter from sliding from "do not omit S" into the opposite universal claim that all selection is unreliable.

Selection Bias Can Also Run the Other Way

In the original twenty-item hypothetical comparison, the entrance admitted more A items, so the visible proportion was higher. If another entrance ran in reverse—taking two of the ten A items and six of the ten non-A items—the proportion of A among the eight visible items would be one quarter, while the population remains one half.

This does not modify Chengwan's achievement rules, nor rewrite the eight-item new comparison onto the original eight cards. It shows only that the effect of selection is not inherently optimistic; an entrance that specializes in collecting experiences of failure may make people more likely to see another kind of outcome. The direction comes from the actual selection relation, not from the word "bias."

Likewise, replacing positive stories with negative ones cannot be called a recovery of the population merely because the attitude is more vigilant. Gu Ning needs to ask how each class enters; pessimism must not be substituted for optimism and passed off as correction. Both kinds of selected material may have particular uses, and both must avoid omitting conditions.

What the reader checks is the range a statement supports, not the author's mood. A superficially neutral tone may still have been given a narrow entrance, and an emphatic account may faithfully describe limited cases; range and correspondence locate this problem better than tone does.

Randomly Drawing Cards from the Cabinet Still Carries the Achievement Threshold

Suppose Gu Ning randomly selects a few cards from the eight achievement cards to examine. The random act operates on objects that have already entered the cabinet. It can prevent her from picking only her favorite cards within the cabinet, but it does not give objects outside the cabinet a chance to enter this examination.

One should therefore state the range from which the random draw was made; writing "random" alone does not mean the full registration is thereby supported. The original production conditions still restrict S in advance; sampling within the cabinet is a later selection. A merit of the later step does not remove the coverage limitation of the earlier entrance.

To study the full registration, one may instead build a search scheme on the registration range and then state how missing original records are handled. This chapter does not design for Gu Ning a finished probability survey, nor guarantee that changing the entrance obtains all information; it only distinguishes where the random act sits.

Multiple selections must be preserved separately. Drawing cards, consulting originals, and admitting items into the count by field correspondence are stages that may connect, but the last, seemingly objective stage must not be allowed to win unexamined representativeness for the entire path.

The Production Instructions and Actual Inclusion Must Also Connect

Ye Cheng's obtaining the production instructions lets Gu Ning know what this entrance originally served, but that does not mean each card's production process has been audited item by item. If actual permissions, photographs, or completion records ever need checking, one must return to the objects, not treat the rule text as an execution record.

It is also possible that the original rule allowed a class of objects but they were not actually included because of where documents were stored or production schedules. Having the opportunity in name and actually entering this batch of material are different levels; an account of actual inclusion can supplement the rules rather than merely repeat the document titles.

This chapter does not claim that execution deviations have been found, nor negate the existing account on the basis of possible deviations. It leaves an interface for further checking: the entrance's use and thresholds are known, while the specific number mapping and other material relations remain incomplete. The adopted range therefore depends on the material obtained, and does not expand just because the institution looks complete.

This keeps the account of selection from both over-promising and resting in vague suspicion. Readers can know which mechanisms have original documentation, which correspondences await checking, and what kind of material would change the current limitation; selection becomes an observable question rather than a permanent label of untrustworthiness attached to all material.

The next round of organizing could preserve the inclusion rules before the target outcomes are seen, noting reasons for later changes. This lets the receiver distinguish original plan, actual execution, and post hoc revision; it does not guarantee the rules themselves are right, but it reduces the room for quietly changing the standard after the outcomes are out. Rules likewise submit to new material and are not forever exempt from reopening merely because they were written down first.

How the Account of the Selection Mechanism Is Delivered

At 2:40 p.m. on Thursday, Gu Ning preserved the account of selection for this stack of achievement cards. The entrance was for objects that were completed, had a displayable photo, and had obtained permission; the eight cards belong to the original sixteen items, but no complete number mapping was established, and no current-window confirmation proportion may be computed for them directly.

The account also preserves the registration range, the range of original records obtained, and the comparable range. Of twelve items the original communications can be found, four are still missing; the five confirmations among the eight comparable items and the B-condition table are still explained independently by their own objects, and the eight display cards are not allowed to impersonate the eight comparable items.

The twenty-item selection count and the tenfold-enlarged comparison are listed separately as hypothetical demonstrations, not added to Chengwan's history. The difference between the visible three quarters and the population one half arises from the admission proportions; it displays the mechanism and is not used as the two ends of a realistic estimate for R17.

RC's theory reduction acknowledges that limited representation requires conditions of selection. Applied to a material collection, selection provides use and order, and may also let the omitted objects exit judgment. What can continue to be generated is the demand that these conditions of exit be stateable and that later material be able to enter—not the demand that there never be any screening.

The judgment reached in this chapter is that genuinely visible material still carries its conditions of admission. Expanding the experience conditional on S into the entire target range requires separately checking representativeness and transport support; it cannot pass automatically on the strength of large numbers, true photographs, or legitimate display.

The next chapter turns to the states that never entered the visible outcome table. Incomplete, not yet at the deadline, out of contact, withdrawn, and missing original records must not be lumped into failure, nor may the unobserved be deleted because the surviving story is uniformly smooth. The selection rule explains the entrance; the outcome states still need a preservation scheme of their own.