Statistics for Data Science & Analytics

This blog post covers essential SAS interview questions to help aspiring data analysts and SAS programmers prepare for technical interviews. It explains core concepts like the basic elements of a SAS program, creating permanent datasets, the role of the DATA step, and how SAS informats work. Each question is answered concisely with practical examples, making it a quick yet comprehensive guide for interview preparation related to SAS Programming.

Essential SAS Interview Questions

What are the Basic Elements needed to run a SAS Program?

To run a SAS program, the following basic elements are needed:

• SAS Software – Install SAS (Base SAS, SAS Studio, or SAS University Edition).
• SAS Program – A SAS Programming Script containing:
  • DATA Step – To create or modify datasets.
  • PROC Step – To analyze or process data (e.g., PROC PRINT, PROC MEANS).
• Input Data – Can be internal (directly in the program) or external (CSV, Excel, etc.).
• Output – Procedure Results (logs, reports, or new datasets).
• SAS Environment – A workspace (SAS Display Manager, SAS Studio, or Enterprise Guide).

To run a SAS program, the following must be followed:

• Every line/statement has a semicolon
• Input statement
• A data statement that defines the data set
• A run statement
• There must be a minimum of one space between each statement or word.

How do you create a Permanent SAD Data Set?

To create a permanent SAS dataset, one must:

1. Assign a Library – Use the LIBNAME statement to link a folder where the dataset will be stored.
2. Reference the Library – Prefix the dataset name with the library name.

Example of Creating a Permanent Dataset in SAS

LIBNAME mylib "C:\SAS\Data";  /* Define a library */  

DATA mylib.permanent_data;  /* Creates a permanent dataset */  
   INPUT ID Name $ Age;  
   DATALINES;  
1 imdad 45  
2 Usman 30  
3 Ali 24
;  
RUN;  

The following are key points to note

• The dataset (permanent_data) is saved in the specified folder (C:\SAS\Data) even after the SAS session ends.
• Without a LIBNAMESAS stores datasets temporarily in the WORK library (deleted after the session).

To access the data for later use:

LIBNAME mylib "C:\SAS\Data";  
PROC PRINT DATA=mylib.permanent_data;  
RUN;  

What is the data step known in SAS?

In SAS, the DATA step is a fundamental programming component used to:

• Create or Modify Datasets – Read, transform, and manipulate data.
• Process Raw Data – Import external files (CSV, Text, and Excel) or create data internally.
• Perform Calculations & Conditional Logic – Using SAS functions, loops (DO-END), and IF-THEN-ELSE statements.
• Clean & Prepare Data – Handle missing values, recode variables, merge datasets, etc.

Key Features of the DATA Step:

• Begins with DATA the statement (names the dataset).
• Use INPUT to define variables.
• Can include SET, MERGE, UPDATE, or INFILE to work with existing data.
• Ends with RUN; (or a subsequent PROC step).

Note that the Data Step is important because

• The core of SAS data manipulation.
• Used before most PROC (procedure) Steps for analysis/reporting.
• Allows complex data transformations before analysis.

What is a SAS Data Set?

A SAS dataset is a structured data file used in SAS programming, organized in a table format with:

• Rows (Observations) – Represent individual records (e.g., customers, transactions).
• Columns (Variables) – Represent data attributes (e.g., ID, Name, Age).

The key Features of a SAS Data Set are:

1. Stored in Libraries –
   • Temporary: WORK library (deleted after session).
   • Permanent: Saved in a user-defined library (e.g., LIBNAME mylib "C:\Data";).
2. Two Parts:
   • Descriptor (metadata like variable names, types).
   • Data (actual values).
3. File Extension: .sas7bdat for datasets, .sas7bcat for catalogs.

A SAS dataset is used for Data storage, manipulation, and analysis in SAS procedures (PROC steps).

What SAS informats are?

SAS informats are instructions used to read raw data (for example, from files or datalines) and convert it into a SAS-readable format. They define how SAS interprets input data (numbers, dates, text, etc.).

The key features of SAS informats are:

• Used in INPUT statements (DATA step) or with INFILE/INFORMAT statements.
• Syntax: INFORMAT variable_name <format>; or embedded in INPUT.
• Common types:
  • Numeric: 8. (standard numeric), COMMA9. (with commas like 1,000).
  • Character: $10. (reads 10 characters).
  • Date/Time: DATE9. (e.g., 01JAN2023), MMDDYY10. (e.g., 01/01/2023).

The following is an example of SAS informats.

DATA example;  
   INPUT @1 Name $10.  @12 DOB MMDDYY10. @23 Salary COMMA9.;  
   DATALINES;  
Imdad      01/01/1990 50,000  
Usman     12/15/1985 75,000  
;  
RUN;  

• $10. reads 10-character text.
• MMDDYY10. reads dates in MM/DD/YYYY format.
• COMMA9. reads numbers with commas (e.g., 50,000).

Describe Some Common SAS Informats.

The common SAS Informats are:

Type	Example Informats	Usage
Numeric	8., COMMA9., PERCENT8.	Reads standard, comma-separated, or percentage numbers
Character	$10., $CHAR20.	Reads fixed-length text
Date	DATE9., MMDDYY10., YYMMDD10.	Converts text to SAS dates
Time	TIME8., DATETIME20.	Reads time/datetime values

Describe when to use SAS Informats.

The SAS informats should be used when:

• Importing external files (CSV, text).
• Reading non-standard data (e.g., dates in different formats).
• Converting raw text into usable SAS variables.

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