CompTIA Data+ (DA0-001) — All Questions

During data preparation, an analyst finds the same customer recorded three times with identical details. Which data-cleansing task removes these repeats?

• a.Imputation
• b.Normalization of numeric ranges
• c.Deduplication✓
• d.Aggregation

Deduplication removes duplicate records so each entity appears once, preventing inflated counts and skewed analysis. Imputation fills in missing values, normalization rescales numeric ranges, and aggregation summarizes groups; none of those address duplicate rows.

A dataset has a numeric column where about 3 percent of values are missing at random. The analyst replaces the missing values with the column's median. What is this technique called?

• a.Imputation✓
• b.Deduplication
• c.Parsing
• d.Encryption

Imputation fills in missing values using a strategy such as the mean, median, or a model-based estimate so that records remain usable. Deduplication removes repeats, parsing splits or extracts fields, and encryption protects confidentiality, none of which replace missing values.

An analyst needs to combine a customer table and an orders table so that each order row is enriched with the matching customer's name using a shared customer ID. Which operation accomplishes this?

• a.A pivot
• b.A histogram
• c.A moving average
• d.A join✓

A join combines rows from two tables based on a related key, such as customer ID, enriching each order with the matching customer details. A pivot reshapes data, a histogram visualizes a distribution, and a moving average smooths a time series; none merge tables on a key.

Before analysis, an analyst reviews a new dataset to summarize its structure, value ranges, null counts, and data types to assess its quality. What is this process called?

• a.Data visualization
• b.Data profiling✓
• c.Data encryption
• d.Data archiving

Data profiling examines a dataset's structure, distributions, ranges, null counts, and types to understand its content and quality before deeper work. Visualization presents findings, encryption protects data, and archiving stores it long-term; none of those characterize the data upfront.

A pipeline extracts data from source systems, transforms it into a consistent format, and then loads it into a data warehouse. Which term describes this sequence?

• a.OLAP
• b.RAID
• c.ETL✓
• d.DNS

ETL stands for extract, transform, load, the classic pattern of pulling data from sources, cleaning and reshaping it, then loading it into a warehouse. OLAP is an analytical query style, RAID is a storage-redundancy scheme, and DNS is a naming system, none of which describe this data pipeline.