Build a lid fault decision table and test it against five described symptoms

applied · 70 min · Objective 1.1

Task

Turn the four lid systems into a decision table that maps a symptom to a component and a confirming test, then run the table against five symptom descriptions and record where it was ambiguous. A table that answers every case is usually a table that is not being honest about ambiguity.

Steps

  1. Write lab/lid/decision.csv with header symptom,component,confirming_test,cost and at least eight rows. cost is free, minutes or parts.
  2. Order the rows so that free tests come before tests requiring parts, and record in lab/lid/ordering.md why that ordering is not the same as ordering by likelihood.
  3. Write five symptom descriptions into lab/lid/cases.txt, one per line, each precise enough to be decidable -- for example 'image present, no touch response, buttons work'.
  4. For each case, record in lab/lid/answers.csv with header case,component,test,ambiguous_with the component your table names, the test, and any other component the symptom could equally indicate. Write none in ambiguous_with when no other component fits. Keep commas out of every field: the Verify splits on them, and one comma shifts every column after it.
  5. At least one of your five cases must be genuinely ambiguous. Record in lab/lid/ambiguity.md what additional observation would resolve it.

Verify

These checks run in a POSIX shell: Terminal on macOS or Linux, and on Windows Git Bash (it comes with Git for Windows) or WSL. A stock Windows PowerShell or Command Prompt has no awk or grep, so there the first line fails.

awk -F, 'NR>1 && NF>=4 {n++} END {print n+0" decision row(s)"}' lab/lid/decision.csv
awk -F, 'NR>1 {print $4}' lab/lid/decision.csv | sort -u | wc -l
grep -c . lab/lid/cases.txt
awk -F, 'NR>1 && NF>=4 {n++} END {print n+0" case(s) answered"}' lab/lid/answers.csv
awk -F, 'NR>1 && $4!="" && $4!="none" {n++} END {print n+0" ambiguous case(s)"}' lab/lid/answers.csv
grep -c . lab/lid/ambiguity.md

Eight or more decision rows across at least two cost bands, five cases, five answers, and at least one ambiguous case with a resolving observation. A table with zero ambiguous cases has not been tested against a hard enough case.

Notes

Keep this table. Lesson 38 builds the display version of the same thing, and lesson 45 collects every table in the course into one symptom-to-tool map.

This is an independent study companion for CompTIA A+ Core 1 220-1201 and is not produced by or endorsed by CompTIA.