Question bank
Pick an answer to see if you're right — with an explanation.
All topicsPythonSQL / MySQLData ScienceNumPyPandasMatplotlibMachine LearningDeep LearningArtificial IntelligenceLarge Language ModelsDjangoAPIsGit & GitHubPower BIExcelStatistics
NumPyEasy
Which operator performs matrix multiplication of two NumPy arrays?
a*
b**
c@
d//
Explanation: `@` (np.matmul) is the matrix product; `*` is element-wise.
PandasEasy
Which method converts a wide table (one column per month) into long format?
amelt
bpivot
cunstack
dexplode
Explanation: melt turns columns into rows of (variable, value) pairs.
Power BIEasy
In a star schema, `Product` (one side) is related to `Sales` (many side) with Single cross-filter direction. Which way do filters flow?
aFrom Product to Sales
bFrom Sales to Product
cIn both directions
dFilters do not propagate across relationships
Explanation: With single direction, the one side filters the many side; selecting a brand filters sales, but not the reverse.
PythonEasy
Which keyword turns a function into a generator?
areturn
basync
clambda
dyield
Explanation: Any function body containing `yield` returns a generator object when called.
SQL / MySQLEasy
Which window function gives the value from the previous row?
aLEAD
bFIRST_VALUE
cPREV
dLAG
Explanation: LAG looks backwards; LEAD looks forwards.
StatisticsEasy
Ice-cream sales and AC sales are highly correlated across months. What is the most likely explanation?
aIce cream causes AC purchases
bAC purchases cause ice-cream sales
cThe correlation must be a data error
dA confounder: hot weather drives both
Explanation: Temperature is a common cause of both, a classic confounding example.
PythonMedium
Which type is immutable?
alist
btuple
cdict
dset
Explanation: Tuples cannot be changed after creation.
SQL / MySQLEasy
Which keyword removes duplicate rows?
aUNIQUE
bDISTINCT
cDIFFERENT
dSINGLE
Explanation: SELECT DISTINCT removes duplicates.
PandasMedium
Which merges two DataFrames on a key?
adf.join_on()
bdf.merge()
cpd.concat()
ddf.combine()
Explanation: merge performs SQL-style joins.
Machine LearningMedium
Best metric for rare fraud detection?
aAccuracy
bRecall / PR-AUC
cR²
dMAE
Explanation: Accuracy is misleading on imbalanced data.
DjangoEasy
Which setting must be False in production?
aUSE_TZ
bDEBUG
cAPPEND_SLASH
dUSE_I18N
Explanation: DEBUG=True leaks sensitive information.
Large Language ModelsMedium
Embeddings are…
aCompressed images
bNumeric vectors representing meaning
cEncrypted text
dModel weights
Explanation: Similar meanings have nearby vectors.
Artificial IntelligenceEasy
Which of these is a computer vision task?
aSentiment analysis of reviews
bMachine translation
cSpeech-to-text transcription
dDetecting helmets in CCTV footage
Explanation: Detection works on image pixels; the other three operate on text or audio.
APIsEasy
What are the three dot-separated parts of a JWT?
akey.value.checksum
buser.role.expiry
cheader.payload.signature
diss.sub.aud
Explanation: A JWT is header.payload.signature, each Base64URL-encoded.
Data ScienceEasy
Which chart best shows how daily sales changed over six months?
aPie chart
bScatter plot
cLine chart
dRadar chart
Explanation: Line charts are the standard choice for trends over time.