◀ 11.4a11.4b11.4c ▶

11.4b — MC Practice 2: Data & Networks

Target practice. Set 2 drills the data families (DAT-1, DAT-2, AAP-1 — binary, lists, filtering) and the network families (CSN-1, CSN-2 — packets, routing, redundancy). These are the questions your 9.1–9.9 units mapped directly, so today is verification: do you score what you learned?

Warm Drill ~10 min

Round the bases, 90 seconds each — write answers, then check neighbors:

(DAT-1) A list of 32 student names — minimum bits to give each a unique ID?
(DAT-2) The dataset column "rating 1–5" — which operation answers "most common rating", and how would you loop it in pseudocode?
(CSN-1) Why can the internet "route around damage"?
(CSN-2) Why is UDP right for game packets and TCP right for the game's download? (9.8)

Check your answers write yours, then compare with your neighbor

Then compare. Every one of these is a family you met earlier this year — the check is whether the words come back with the lesson closed.

(DAT-1) 2⁵ = 32, so 5 bits — five bits to name 32 students, not thirty-two bits.
(DAT-2) The mode: a tally per value, then take the largest. One counter per rating, one loop over the rows to fill them, one pass over the counters to find the biggest.
(CSN-1) No single path: packets re-route, because a router decides locally instead of reading a map of the whole network.
(CSN-2) Drop vs. wait (9.8): UDP drops a late packet and keeps the game moving; TCP holds the download until every packet arrives, because half a download is worth nothing.

Practice Set 218 questions, 18 min

18 questions in 18 minutes. Data (DAT-1, DAT-2, AAP-1) and networks (CSN-1, CSN-2). Answer every question — there is no penalty for guessing, and a blank scores like a wrong one. When the timer stops, press Grade this set for your scorecard and the family error table.

1. What decimal value does the binary number 1011 represent?DAT-1

A11B13C1011D22

2. A palette has exactly 12 distinct colors. What is the minimum number of bits needed to store one color selection?DAT-1

A3B4C12D24

3. Why does an MP3 file usually sound slightly different from the original recording, while a ZIP archive of the same recording does not?DAT-1

AMP3 uses lossy compression and permanently discards some audio detail; ZIP uses lossless compression and preserves every bitBMP3 uses lossless compression but plays back at a lower volumeCZIP compresses audio more aggressively than MP3 doesDBoth are lossy, but MP3 loses less detail

4. A program stores a count in an 8-bit unsigned integer. The count is currently 255 and the program adds 1. What happens?DAT-1

AThe count becomes 256 and is stored correctlyBThe count overflows — there is no 9th bit to hold the carry, so the stored value wraps (commonly to 0)CThe program automatically upgrades the variable to a larger typeDThe count becomes negative because the sign bit flips

5. A researcher removes all rows with missing values from a survey dataset before analyzing it. Which is the most accurate description of the effect?DAT-2

AThe dataset becomes strictly more accurate because incomplete records are unreliableBThe dataset becomes cleaner but potentially less representative, because the removed rows may share a characteristic that affects the resultCThe dataset is unaffected because missing values carry no informationDThe dataset becomes less accurate and less clean

6. A dataset of 10,000 game sessions includes, for each session, the player's country, the session length in seconds, whether they bought an item, and the device model. Which of these is metadata rather than the primary data being analyzed?DAT-2

AThe session length in secondsBWhether the player bought an itemCThe device model recorded alongside each sessionDNone of these — all four are primary data

7. A study finds that students who eat breakfast score higher on tests. A news headline reports "Breakfast causes higher test scores." What is the most significant problem with the headline?DAT-2

AThe sample size was not reportedBA correlation between two variables does not establish that one causes the otherCTest scores are not numerical dataDThe study should have used a larger range of breakfasts

8. What is displayed?AAP-1

x ← 3
y ← x
x ← 7
DISPLAY(y)

A3B7C10DNothing — the program errors

9. What is the value of result?AAP-1

a ← 10
b ← 4
result ← a / b + MOD(a, b)

A4.5B2.5C2D6.5

10. A program must track a player's name, score, and remaining lives together for 50 players. Which approach best uses data abstraction?AAP-1

AThree separate lists of 50 elements each, kept in matching orderBA single list of 50 records, where each record holds a name, a score, and a life countC150 individual variables named player1Name, player1Score, and so onDA single string containing all the data separated by commas

11. What is displayed?AAP-1

greeting ← "Hello"
name ← "Ada"
DISPLAY(greeting + ", " + name)

AHello AdaBHello, AdaCHelloAdaDAn error — strings cannot be joined

12. A gaming company doubles the bandwidth of its servers. Players in one region still report high ping. Which explanation is most consistent with this outcome?CSN-1

ABandwidth and latency are the same thing, so the claim is impossibleBMore bandwidth per second does not reduce the time each individual packet takes to travel, so latency is unchangedCDoubling bandwidth always increases latency because of the extra dataDThe servers must be running out of storage

13. The internet continues to deliver traffic when individual routers fail or cables are cut. Which design choice explains this?CSN-1

AEvery message is sent twice, and the second copy is discardedBPackets are routed independently, so a failed path can be routed around rather than blocking the messageCEach user connects directly to a single central serverDData is compressed so that fewer cables are required

14. A message is split into packets that arrive at the destination out of order. What allows the original message to be reconstructed correctly?CSN-1

AThe packets are re-sent in the correct order by the network until they arrive sequentiallyBEach packet carries information identifying the message it belongs to and its position, so the destination can reassemble them in orderCThe destination discards out-of-order packets and requests the whole message againDOut-of-order packets are not possible on the internet

15. A small company runs its entire website, email, and file storage on a single physical server in its office. Which statement best describes the risk?CSN-1

AThe company has excellent fault tolerance because everything is in one placeBThe server is a single point of failure — one power outage or disk failure takes down every service at onceCThe company's data is safe because a single server is easier to encryptDThere is no risk, because one server is simpler to maintain

16. A user visits a site over HTTPS and sees the padlock icon. What does this guarantee?CSN-2

AThe site is operated by a trustworthy organizationBThe connection to the site is encrypted, so data in transit cannot be read by a third partyCThe site will not contain malwareDThe site's content has been fact-checked

17. What is the primary purpose of the Domain Name System (DNS)?CSN-2

ATo encrypt traffic between a user and a websiteBTo translate human-readable domain names into the IP addresses computers use to route trafficCTo compress web pages so they load fasterDTo store copies of websites in case the original fails

18. A multiplayer game sends each player's position to the server many times per second. A missed update is acceptable because a newer one follows immediately; waiting for a lost one would cause visible stutter. Which protocol characteristic fits this need?CSN-2

AA protocol that guarantees every packet arrives in order, even if delivery is delayedBA protocol that prioritizes speed and accepts that occasional packets may be lostCA protocol that encrypts each packet separatelyDA protocol that compresses positions before sending them

0/18 answered

Your answers save on this device and are included in the answers .json you download at the end of the lesson.

Error Table v2 & Pair-Teach ~25 min

Grade the set, then work the table:

Grade → error table v2 (family / time / right-wrong), cumulative with Set 1
Compare to Set 1: did the weak family improve? If not — WHY not (misconception, not speed: wrong tells you what to re-read)
The misconception hunt: for each wrong answer, write the sentence of what you BELIEVED. "The mode is the average" is a fixable sentence; "I guessed C" is not.

Pair-teach (10 min): find someone whose error table is strong where yours is weak. They explain their attack on 2 questions; you explain yours. Teaching is the fastest known study method — this is 1.1's pair setup running one last time.

Socratic: Tagging the Misses

You tagged your misses by CED family. Which family did you think you knew, and what does the tag say?Your answer
Bandwidth and latency are the classic trap pair. In your own words, which one does a bigger file hurt, and which one does distance hurt?Your answer
You paired up to teach an error back. Which explanation changed your own answer — explaining it, or being explained to?Your answer

Checkpoint — before moving on, you must be able to:

Score Set 2 with a family-labeled error table
Write the misconception sentence for every miss
Teach one question to someone whose table is weak there
Know which families you'll drill before 11.4c

Reference Docs

Need a deeper explanation? These pages cover the same concepts:

Binary & Hex — DAT-1 family
The Internet — CSN-1/CSN-2 family
MC Strategy — three-pass reminder

Next: 11.4c — MC Practice 3 + Written-Response Drill

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