PCED Exam Prep — Mock Exam & Review

• Understand PCED format and what it tests.
• Take a 10-question mock under time.
• Score yourself; identify weak topics.
• Write a one-week study plan.

PCED (Python Certified Entry-Level Data Analyst)

Format     : ~30 multiple-choice questions
Time       : 45-60 minutes (check the latest spec)
Pass mark  : ~70%
Topics     :
  - Python basics (Level 1-2 ground)
  - pandas: loading, selecting, filtering, grouping, merging
  - matplotlib basics
  - statistics (mean, median, stdev, percentiles)
  - data cleaning (missing values, dtypes)
  - file I/O (CSV, JSON)
  - datetime operations

Set a timer for 15 minutes. Do not look up answers.

Q1. What does this return?

import pandas as pd
df = pd.DataFrame({"a": [1, 2, 3], "b": [4, 5, 6]})
df.iloc[1, 1]

(A) 1 · (B) 4 · (C) 5 · (D) 6

Q2. Which mask keeps only rows where b is > 4?

(A) df[df.b > 4] · (B) df.where(df.b > 4) · (C) df.b > 4 alone · (D) df.filter(df.b > 4)

Q3. How do you count missing values per column?

(A) df.count() · (B) df.isna().sum() · (C) df.missing() · (D) df.nan_count()

Q4. Result of statistics.median([1, 2, 3, 4])?

(A) 2 · (B) 2.5 · (C) 3 · (D) 1

Q5. Which kwarg controls indentation in json.dump?

(A) tab= · (B) indent= · (C) pretty= · (D) spaces=

Q6. Which produces a Series, not a DataFrame?

(A) df[["a"]] · (B) df["a"] · (C) df.loc[:, ["a"]] · (D) df.iloc[:, [0]]

Q7. pd.read_csv("x.csv") reads the first row as:

(A) The first data row · (B) The header · (C) Ignored · (D) An index

Q8. Which is the "split-apply-combine" tool?

(A) df.merge() · (B) df.groupby() · (C) df.concat() · (D) df.pivot()

Q9. Which is correct way to add days to a date?

from datetime import date, timedelta
d = date(2026, 5, 28)

(A) d + 5 · (B) d.add(5) · (C) d + timedelta(days=5) · (D) d.plus_days(5)

Q10. Output?

import pandas as pd
s = pd.Series([10, 20, 30, 40])
s.mean()

(A) 20 · (B) 25 · (C) 30 · (D) 100

Q1.  (C) 5            iloc is (row, col) 0-indexed → row 1, col 1 = b[1] = 5
Q2.  (A)              df[mask] keeps True rows
Q3.  (B)              isna().sum() — the standard idiom
Q4.  (B) 2.5          median of even count = average of the two middle
Q5.  (B) indent=      same kwarg in dump and dumps
Q6.  (B) df["a"]      single brackets → Series; double brackets → DataFrame
Q7.  (B) header       read_csv assumes the first row is column names
Q8.  (B) groupby      that's the textbook phrase for groupby
Q9.  (C)              date + timedelta is the only valid pattern
Q10. (B) 25           (10+20+30+40)/4 = 25

Scoring

• 9–10 right: ready for the exam.
• 7–8: pass-likely. Re-read the lessons covering your wrong answers.
• 5–6: another week of revision. Do every Try-It from L4-25 onward.
• ≤ 4: walk through L4-25 to L4-46 again, slowly. The PCED is a fluency exam — fluency comes from repetition.

For each topic where you missed a question, do the matching drill:

• iloc / loc / brackets → re-do Lesson 26 exercises.
• Filtering → re-do Lesson 27.
• Missing values → re-do Lesson 29.
• Stats → re-do Lesson 46.
• JSON / CSV → re-do Lessons 01–05.
• groupby → re-do Lesson 28.
• Dates → re-do Lesson 06.

Don't just re-read — re-type the code from memory. Fluency comes from your fingers, not your eyes.

Level 4 done. You can:

• Read & write JSON and CSV; clean messy data.
• Call REST APIs and scrape HTML responsibly.
• Design schemas, write SQL, use SQLite from Python.
• Wrangle DataFrames — load, select, filter, group, merge, clean, sort.
• Draw bar / line / pie / scatter / subplot charts.
• Ship a Flask app with SQLite, auth, and a public URL.
• Reason about data ethics and present honest charts.

That's the bulk of a junior-developer skill set. Level 5 picks up here with machine learning, neural nets, computer vision, and LLM APIs.