Top 100 SAS Interview Questions and Answers for 2024

Are you preparing for a SAS interview? If yes, you’re in the right place! SAS (Statistical Analysis System) is a powerful software suite widely used for advanced analytics, data management, and predictive modeling across various industries. In this article, we’ll cover the top 100 SAS interview questions and answers to help you ace your interview and land your dream job.

What is SAS?

SAS is a statistical software suite that provides a user-friendly interface for data access, data management, advanced analytics, business intelligence, and predictive analytics. It was developed by the SAS Institute and is widely used in various sectors, including healthcare, finance, marketing, and academia.

Why is SAS Important?

• Easy to Learn: SAS is relatively easy to learn, especially for individuals already familiar with SQL, as it provides an option called PROC SQL.
• Data Handling Capabilities: SAS is on par with leading tools like R and Python when it comes to handling large datasets and offering parallel computing options.
• Graphical Capabilities: SAS provides robust graphical capabilities, and with some learning, you can customize plots according to your requirements.
• Job Opportunities: Globally, SAS is a market leader in available corporate jobs related to data analytics. In India, SAS controls about 70% of the data analytics market share.

Now, let’s dive into the top SAS interview questions and answers.

SAS Interview Questions and Answers

Basic SAS Interview Questions

1. What are the features of SAS?

   • Business Solutions: SAS provides business analysis tools for various companies.
   • Analytics: SAS is a market leader in analytics for business products and services.
   • Data Access & Management: SAS can be used as a Database Management System (DBMS) software.
   • Reporting & Graphics: SAS helps visualize analysis in the form of summary reports, lists, and graphics.
   • Visualization: SAS allows you to visualize reports as graphs, ranging from simple scatter plots and bar charts to complex multi-page classification panels.

2. Mention a few capabilities of the SAS Framework.

   • Access: SAS allows you to access data from multiple sources, such as Excel files, raw databases, Oracle databases, and SAS datasets.
   • Manage: You can manage data by subsetting, creating variables, validating, and cleaning it.
   • Analyze: SAS is the gold standard for statistical analyses, allowing you to perform simple analyses like frequency and averages, as well as complex analyses like regression and forecasting.
   • Present: You can present your analysis in the form of lists, summaries, and graphic reports, which can be printed, written to data files, or published online.

3. What is the function of the OUTPUT statement in a SAS program?
   The OUTPUT statement is used to save summary statistics in a SAS dataset. This information can be used to create customized reports or save historical data about a process. You can use options in the OUTPUT statement to specify the statistics to save, the name of the output dataset, and compute and save percentiles not automatically computed by the procedure.

4. What is the function of the STOP statement in a SAS program?
   The STOP statement causes SAS to stop processing the current data step immediately and resume processing statements after the end of the current data step.

5. What is the difference between using DROP = dataset option in the DATA statement and the SET statement?

   • If you don’t want to process certain variables and don’t want them to appear in the new dataset, specify the DROP = dataset option in the SET statement.
   • If you want to process certain variables but don’t want them to appear in the new dataset, specify the DROP = dataset option in the DATA statement.

6. How do you read the last observation to a new dataset from an unsorted dataset?
   To read the last observation to a new dataset from an unsorted dataset, use the END= dataset option. For example:

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   data work.calculus;set work.comp end=last;if last;run;

   Here, calculus is the new dataset to be created, comp is the existing dataset, and last is a temporary variable (initialized to 0) that is set to 1 when the SET statement reads the last observation.

7. What is the difference between reading data from an external file and reading data from an existing dataset?
   The main difference is that when reading an existing dataset with the SET statement, SAS retains the values of the variables from one observation to the next. However, when reading data from an external file, only the observations are read, and the variables will need to be re-declared if they need to be used.

8. How many data types are there in SAS?
   There are two data types in SAS: character and numeric. Apart from these, dates are also considered characters, although there are implicit functions to work with dates.

9. What is the difference between SAS functions and procedures?

   • Functions expect argument values to be supplied across an observation in a SAS dataset.
   • A procedure expects one variable value per observation.

   For example:

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   data average;set temp;avgtemp = mean(of T1 - T24);run;

   Here, the arguments of the mean function are taken across an observation. The mean function calculates the average of the different values in a single observation.

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   proc sort;by month;run;proc means;by month;var avgtemp;run;

   The PROC MEANS procedure is used to calculate the average temperature by month, taking one variable value across an observation.

10. What are the differences between the SUM function and using the “+” operator?
    The SUM function returns the sum of non-missing arguments, whereas the “+” operator returns a missing value if any of the arguments are missing.

    Example:

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    data mydata;input x y z;cards;33 3 324 3 424 3 4. 3 223 . 354 4 .35 4 2;run;data mydata2;set mydata;a = sum(x, y, z);p = x + y + z;run;

    In the output, the value of p is missing for the 4th, 5th, and 6th observations because one or more arguments are missing.

Intermediate SAS Interview Questions

1. What are the differences between PROC MEANS and PROC SUMMARY?

   • PROC MEANS produces subgroup statistics only when a BY statement is used, and the input data has been previously sorted (using PROC SORT) by the BY variables.
   • PROC SUMMARY automatically produces statistics for all subgroups, giving you all the information in one run that you would get by repeatedly sorting a dataset by the variables that define each subgroup and running PROC MEANS.
   • PROC SUMMARY does not produce any information in your output, so you will need to use the OUTPUT statement to create a new dataset and use PROC PRINT to see the computed statistics.

2. Give an example where SAS fails to convert a character value to a numeric value automatically.
   Suppose the value of a variable PayRate begins with a dollar sign ($). When SAS tries to automatically convert the values of PayRate to numeric values, the dollar sign blocks the process, and the values cannot be converted to numeric values. Therefore, it is always best to include INPUT and PUT functions in your programs when conversions occur.

3. How do you delete duplicate observations in SAS?
   There are three ways to delete duplicate observations in a dataset:

   1. By using NODUPS in the procedure:

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      proc sort data=SAS-Dataset nodups;by var;run;

   2. By using an SQL query inside a procedure:

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      proc sql;create SAS-Dataset asselect * from Old-SAS-Datasetwhere var=distinct(var);quit;

   3. By cleaning the dataset:

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      set temp;by group;if first.group and last.group thenrun;

4. How does PROC SQL work?
   When PROC SQL is executed, the following steps happen:

   1. SAS scans each statement in the SQL procedure and checks for syntax errors, such as missing semicolons and invalid statements.
   2. The SQL optimizer scans the query inside the statement and decides how the SQL query should be executed to minimize run time.
   3. Any tables in the FROM statement are loaded into the data engine, where they can be accessed in memory.
   4. Code and calculations are executed.
   5. The final table is created in memory.
   6. The final table is sent to the output table described in the SQL statement.

5. Briefly explain the INPUT and PUT functions.

   • INPUT function: Used for character-to-numeric conversion. Syntax: input(source, informat)
   • PUT function: Used for numeric-to-character conversion. Syntax: put(source, format)

6. What would be the result of the following SAS function (given that December 31, 2000, is Sunday)?

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   weeks = intck('week', '31dec2000'd, '01jan2001'd);years = intck('year', '31dec2000'd, '01jan2001'd);months = intck('month', '31dec2000'd, '01jan2001'd);

   Here, we calculate the weeks between December 31, 2000, and January 1, 2001. Since December 31, 2000, was a Sunday, January 1, 2001, will be a Monday in the same week. Hence:

   • weeks = 0
   • years = 1, since both days are in different calendar years
   • months = 1, since both days are in different months of the calendar

7. Suppose the variable address stores the following expression: 209 RADCLIFFE ROAD, CENTER CITY, NY, 92716. What would be the result returned by the SCAN function in the following cases?

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   a = scan(address, 3);b = scan(address, 3, ',');

   • a = Road
   • b = NY

8. What is the length assigned to the target variable by the SCAN function?
   The SCAN function assigns a length of 200 to the target variable.

9. Name a few SAS functions.
   Some commonly used SAS functions are:

   • SCAN
   • SUBSTR
   • TRIM
   • CATX
   • INDEX
   • TRANWRD
   • FIND
   • SUM

10. What is the purpose of the TRANWRD function?
    The TRANWRD function replaces or removes all occurrences of a pattern of characters within a character string.

11. Consider the following SAS program:

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    data finance.earnings;amount = 1000;rate = .075 / 12;do month = 1 to 12;    earned + (amount + earned) * (rate);end;run;

    What would be the value of month at the end of the data step execution, and how many observations would there be?

    • The value of month would be 13.
    • There would be 12 observations.

12. Consider the following SAS program:

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    data finance;amount = 1000;rate = .075 / 12;do month = 1 to 12;    earned + (amount + earned) * (rate);    output;end;run;

    How many observations would there be at the end of the data step execution?

    There would be 12 observations.

13. How do you use the DO loop if you don’t know how many times you should execute the DO loop?
    You can use DO UNTIL or DO WHILE to specify the condition.

14. What is the difference between DO WHILE and DO UNTIL?
    An important difference between the DO UNTIL and DO WHILE statements is that the DO WHILE expression is evaluated at the top of the DO loop. If the expression is false the first time it is evaluated, then the DO loop never executes. On the other hand, DO UNTIL executes at least once.

15. How do you specify the number of iterations and a specific condition within a single DO loop?

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    data work;do i = 1 to 20 until(sum >= 20000);    year + 1;    sum + 2000;    sum + sum * .10;end;run;

    This iterative DO statement enables you to execute the DO loop until sum is greater than or equal to 20000 or until the DO loop executes 20 times, whichever occurs first.

16. What are the parameters of the SCAN function?
    The SCAN function is used with the following syntax:

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    scan(argument, n, delimiters)

    Here:

    • argument specifies the character variable or expression to scan
    • n specifies which word to read
    • delimiters are special characters that must be enclosed in single quotation marks

17. If a variable contains only numbers, can it be a character data type?
    Yes, it depends on how you use the variable. There are some numbers we want to use as a categorical value rather than a quantity. For example, a variable called “Foreigner” where the observations have the value “0” or “1” representing “not a foreigner” and “foreigner,” respectively. Similarly, the ID of a particular table can be in numbers but does not represent any quantity. Phone numbers are another popular example.

18. If a variable contains letters or special characters, can it be a numeric data type?
    No, it must be a character data type.

19. What can be the size of the largest dataset in SAS?
    The number of observations is limited only by the computer’s capacity to handle and store them. Prior to SAS 9.1, SAS datasets could contain up to 32,767 variables. In SAS 9.1, the maximum number of variables in a SAS dataset is limited by the resources available on your computer.

20. Give some examples where PROC REPORT’s defaults are different than PROC PRINT’s defaults.

    • No record numbers in PROC REPORT
    • Labels (not variable names) are used as headers in PROC REPORT
    • PROC REPORT needs the NOWINDOWS option

21. Give some examples where PROC REPORT’s defaults are the same as PROC PRINT’s defaults.

    • Variables/Columns are in position order
    • Rows are ordered as they appear in the dataset

22. What is the purpose of the trailing @ and @@? How do you use them?

    • The trailing @ is also known as a column pointer. By using the trailing @ in the INPUT statement, you can read part of your raw data line, test it, and then decide how to read additional data from the same record.
    • The single trailing @ tells the SAS system to “hold the line.”
    • The double trailing @@ tells the SAS system to “hold the line more strongly.” An INPUT statement ending with @@ instructs the program to release the current raw data line only when there are no data values left to be read from that line. The @@ holds the input record even across multiple iterations of the data step.

23. What is the difference between an order variable and a group variable in PROC REPORT?

    • If the variable is used as a group variable, rows that have the same values are collapsed. Group variables produce a list report.
    • An order variable produces a summary report.

24. Give some ways by which you can define the variables to produce a summary report using PROC REPORT.
    All variables in a summary report must be defined as group, analysis, across, or computed variables.

25. What are the default statistics for the MEANS procedure?
    The default statistics for the MEANS procedure are:

    • n (count)
    • mean
    • standard deviation
    • minimum
    • maximum

26. How do you limit decimal places for a variable using PROC MEANS?
    You can use the MAXDEC= option to limit the decimal places for a variable.

27. What is the difference between the CLASS statement and the BY statement in PROC MEANS?