Chapter 16 — Exercises

Work these in order; they climb from recall to real diagnosis. You will need a live web browser and, ideally, a website you can inspect (your own, your employer's, or a client's) plus the free PageSpeed Insights tool at pagespeed.web.dev. Nothing here costs anything. Items marked with a dagger (†) have full worked solutions in Appendix — Answers to Selected Exercises; odd-numbered items are worked there too. Attempt every item before you look.

A reminder in the spirit of the chapter: the goal is never a green score. It is a fast, stable, responsive experience for the real human on the slow phone — with the ranking nudge riding along as a bonus.

A. Recall and vocabulary

Exercise 16.1 — Name the three Core Web Vitals, expand each acronym, say in one plain phrase what each measures, and give its "good" threshold.

Exercise 16.2 — Define field data and lab data in your own words. Then finish the sentence: "For the ranking question, Google uses __ data, so I should believe the ____ result."

Exercise 16.3 — What is CrUX, and what do "75th percentile" and "trailing 28 days" mean about the number it reports for your page?

Exercise 16.4 † — Define TTFB. Explain, in two sentences, why a slow TTFB puts a ceiling on how good your LCP can be.

Exercise 16.5 — What is a render-blocking resource, which vital does it most directly hurt, and name two ways to reduce its impact?

Exercise 16.6 — In one sentence each, distinguish what PageSpeed Insights shows at the top of its report from what it shows below — and say which of the two is Google's ranking signal.

B. Applied reasoning

Exercise 16.7 — The chapter insists on "users first, rankings second." Restate that argument in your own words, and give the one sentence you would say to a boss who asks, "But will fixing speed get us to #1?"

Exercise 16.8 — Explain why your own experience of your website ("it's fast for me") is "the single most misleading test rig in all of SEO." What specifically is different about the real users the metrics measure?

Exercise 16.9 † — In 2024, Google replaced First Input Delay (FID) with INP as a Core Web Vital. Explain what FID missed that INP captures, and why this switch is a good example of the book's third theme (evidence over folklore).

Exercise 16.10 — A colleague says, "Caching plugins are the answer to Core Web Vitals — install one and you're done." Name one vital a caching plugin genuinely helps and two vitals it does little or nothing for, and say why.

Exercise 16.11 — The chapter calls Core Web Vitals "a tiebreaker, not a trump card." Explain what a tiebreaker signal is, and describe a situation where a page with worse Core Web Vitals should still — correctly — outrank a page with better ones.

Exercise 16.12 — Why does the chapter say to "aim for the threshold, not the maximum"? What is the SEO return on pushing a page from a "good" Core Web Vitals result to a perfect lab score?

Exercise 16.13 — Rewrite this sentence so it is honest by the book's standards: "Our page hit a 100 PageSpeed score, so we're guaranteed to rank #1 for our main keyword."

Exercise 16.14 — INP is described as the vital that "punishes feature creep." Explain the mechanism (what is the "main thread," and how does a chat widget or review script cause a laggy tap?).

C. Diagnose the failing vital

For each symptom, name the most likely failing Core Web Vital (LCP, INP, or CLS) and the first fix you would investigate. Some have more than one defensible answer — say why.

Exercise 16.15 † — Users report the page "looks loaded fast" and "never jumps," but the booking button "doesn't work the first time you tap it." Which vital, and what is the likely cause?

Exercise 16.16 † — On a phone over a normal network, the hero photo takes about four seconds to appear, and until it does the top of the page is mostly blank. Which vital, and name the two most likely culprits.

Exercise 16.17 — A reader goes to tap a link in an article; an image finishes loading above it, everything jumps down, and they tap an ad instead. Which vital, and what is the one-line fix?

Exercise 16.18 — A page's field data shows LCP 4.6 s (poor). The breakdown shows TTFB 1.9 s, then a short resource load, then a fast render. Where is the problem concentrated, and which fixes from §16.6 apply?

Exercise 16.19 — A single-page web app feels instant to the developer on their laptop but scores "poor" INP in the field. Give two reasons the field result differs from the developer's experience.

Exercise 16.20 — A page's images are all set with explicit width and height, yet CLS is still "needs improvement." Name two non-image causes of layout shift the team should check next.

D. On your own site (use a free tool)

Exercise 16.21 † — Run your slowest important page through PageSpeed Insights (pagespeed.web.dev), Mobile tab. Record, in order: (a) did the field-data Core Web Vitals assessment Pass or Fail, and which of the three is red; (b) the LCP, INP, and CLS values; (c) the lab performance score. Write one sentence stating your real problem (from the field data), not the lab score.

Exercise 16.22 — For the same page, scroll to the Lighthouse "Opportunities" and "Diagnostics" sections and copy down the top three named recommendations (e.g., "eliminate render-blocking resources," "properly size images," "reduce initial server response time"). Map each to the vital it would help.

Exercise 16.23 — Do the qualitative CLS test from §16.4: on your phone, on a non-office network, open your homepage fresh (private window) and watch the first two seconds. Does anything jump? Try to tap a top link the instant it appears. Write one sentence on what shifted and what you would reserve space for.

Exercise 16.24 — If you have Google Search Console access, open the Core Web Vitals report and record how many URLs are "Good," "Needs improvement," and "Poor" on mobile. Which page group/template has the most failing URLs? (If you have no access, note that setting up Search Console is the Chapter 27 task and write down when you will do it.)

E. Read the report

Exercise 16.25 † — Interpret this report excerpt.

FIGURE E.16 — "Field passes, lab frowns"                        [constructed teaching example]
  FIELD DATA (CrUX, mobile):  Core Web Vitals — PASSED.  LCP 2.2 s · INP 170 ms · CLS 0.05
  LAB DATA (Lighthouse):      Performance score 68 / 100.  Opportunities: "reduce unused JavaScript,"
                              "serve images in next-gen formats."

Should this page's owner spend the afternoon chasing the 68 up toward 100? Answer using the field/lab distinction, and say what — if anything — you would actually do.

Exercise 16.26 — Interpret this excerpt and give a prioritized, two-item action list.

FIGURE E.17 — "Three reds on mobile"                            [constructed teaching example]
  FIELD DATA (CrUX, mobile):  Core Web Vitals — FAILED.
    LCP 5.1 s (poor)   INP 260 ms (needs improvement)   CLS 0.28 (poor)
  Notes: hero image is a 3 MB PNG and is lazy-loaded; page loads 9 third-party scripts; images unsized.

Which vital would you fix first for the biggest, cheapest win, and why? What is the second move?

F. Myths, ethics, and judgment

Exercise 16.27 — Spot the myth. A vendor's landing page claims: "Our plugin gets you a perfect 100 PageSpeed score — the #1 ranking factor — so you'll dominate Google." Identify three separate falsehoods bundled in that sentence and replace each with what the chapter says is true.

Exercise 16.28 — An agency offers a "Core Web Vitals guarantee": pay them, and they promise a top-three ranking once your score is green. Using the chapter's model of ranking and the honest weight of Core Web Vitals, explain in three sentences why no honest practitioner can promise that — and what they can honestly promise.

G. The Strategy File (Rivertown Home Services)

Exercise 16.29 † — Below is a fragment of Rivertown's mobile measurement pass. For each template, name the failing vital(s) and the single highest-leverage fix: (a) Homepage — LCP 4.1 s, CLS 0.18: heavy hero, shifting promo bar. (b) "AC repair" service page — INP 240 ms: nine plugins, several third-party scripts. (c) Location pages — "insufficient field data." For (c), explain why this is not a speed problem you can fix with a CDN, and which chapter actually owns it.

Exercise 16.30 — Do Rivertown's Chapter 16 Strategy-File task on your own (or a client's) site: run PageSpeed Insights (mobile) on your top three templates, record the field-data pass/fail and the failing vital for each, diagnose the shared root causes, and write a prioritized fix list ordered by impact × effort (quick shared wins — caching/CDN, image sizing — before deep per-page work). Do not implement anything yet; the deliverable is a measured, prioritized punch list.

Where these go next. Keep your answers to 16.21, 16.24, 16.29, and 16.30 — they are the Core Web Vitals page of your running Strategy File (Appendix C's worksheet). You will fold them into the full technical audit in Chapter 38 and the complete strategy in Chapter 40.