25 SAS Interview Questions and Answers

SAS (Statistical Analysis System) is a powerful software suite used for advanced analytics, business intelligence, data management, and predictive analytics. Known for its robust data handling capabilities and extensive library of statistical functions, SAS is a staple in industries such as healthcare, finance, and marketing. Its ability to handle large datasets and perform complex analyses makes it an invaluable tool for data professionals.

This article aims to prepare you for SAS-related interview questions by providing a curated selection of queries and detailed answers. By familiarizing yourself with these questions, you will gain a deeper understanding of SAS functionalities and enhance your ability to articulate your expertise during interviews.

SAS Interview Questions and Answers

1. What is the purpose of the DATA step and PROC step in SAS?

In SAS, the DATA step is used for data manipulation, such as reading, transforming, and creating datasets. It allows operations like merging, filtering, and calculating new variables.

Example:

DATA new_dataset;
    SET old_dataset;
    new_variable = old_variable * 2;
    IF new_variable > 10 THEN output;
RUN;

The PROC step is for data analysis and reporting, including statistical analysis and generating reports. Common procedures include PROC MEANS, PROC FREQ, and PROC REG.

Example:

PROC MEANS DATA=new_dataset;
    VAR new_variable;
RUN;

2. Explain the use of the INFILE statement.

The INFILE statement specifies an external file to read data from, often used in data steps to convert raw data files into SAS datasets. It provides options to control data reading, such as delimiters and handling missing values.

Example:

data mydata;
    infile 'path/to/your/file.txt' dlm=',' missover;
    input var1 var2 var3;
run;

3. What is the difference between a FORMAT and an INFORMAT in SAS?

In SAS, FORMAT and INFORMAT control data display and input, respectively. An INFORMAT interprets raw data values when read into a dataset, while a FORMAT presents data values in the output.

4. How would you merge two datasets by a common variable in SAS?

Merging datasets by a common variable is done using the DATA step with the MERGE statement. The common variable aligns observations from different datasets.

Example:

data dataset1;
    input id name $;
    datalines;
    1 John
    2 Jane
    3 Alice
    ;
run;

data dataset2;
    input id age;
    datalines;
    1 25
    2 30
    4 22
    ;
run;

data merged_dataset;
    merge dataset1(in=a) dataset2(in=b);
    by id;
    if a and b;
run;

5. Describe how to create a new variable in a SAS dataset.

Creating a new variable in a dataset is done within a DATA step using an assignment statement.

Example:

DATA new_dataset;
    SET original_dataset;
    new_variable = existing_variable * 2;
RUN;

6. Explain the use of the PROC MEANS procedure in SAS.

PROC MEANS generates descriptive statistics for numeric variables, calculating measures like mean, median, and standard deviation.

Example:

proc means data=sashelp.class;
   var age height weight;
run;

7. Describe the use of the BY statement in SAS.

The BY statement groups data for processing, requiring data to be sorted by specified variables. It allows operations on subsets of data.

Example:

proc sort data=mydata;
    by group;
run;

proc means data=mydata;
    by group;
    var value;
run;

8. How do you create a macro variable in SAS?

Macro variables store text for reuse in SAS programs, created using the %LET statement or within a macro definition.

Example using %LET statement:

%let var_name = value;

data example;
    set dataset;
    new_var = &var_name;
run;

Example within a macro definition:

%macro example_macro;
    %let var_name = value;

    data example;
        set dataset;
        new_var = &var_name;
    run;
%mend example_macro;

%example_macro;

9. What is the purpose of the %LET statement in SAS?

The %LET statement defines macro variables, storing text or numeric values for dynamic code.

Example:

%LET var = age;

proc print data=sashelp.class;
    var &var;
run;

10. How do you debug a program in SAS?

Debugging in SAS involves using the LOG window, OPTIONS statement, PUT statement, PROC PRINT, PROC CONTENTS, and the Data Step Debugger to identify and resolve errors.

• LOG Window: Provides detailed execution information, including notes, warnings, and error messages.
• OPTIONS Statement: Enhances debugging with options like MPRINT, SYMBOLGEN, and MLOGIC.
• PUT Statement: Writes custom messages to the LOG window for tracking data flow and variable values.
• PROC PRINT and PROC CONTENTS: Display dataset contents and attributes for verification.
• Data Step Debugger: Allows interactive stepping through data step code.
• Error Handling: Use the ERRORCHECK option for managing errors.

11. Explain the use of the PROC SQL procedure in SAS.

PROC SQL executes SQL queries for data manipulation and retrieval, allowing complex data operations in a single step.

Example:

proc sql;
   create table summary as
   select name, 
          sum(sales) as total_sales
   from sales_data
   where region = 'North'
   group by name;
quit;

12. How do you join tables using PROC SQL in SAS?

Joining tables using PROC SQL involves combining data from multiple tables based on a related column.

Example:

proc sql;
    select a.*, b.*
    from table1 as a
    inner join table2 as b
    on a.common_column = b.common_column;
quit;

13. Describe the use of the ARRAY statement in SAS.

The ARRAY statement defines a group of variables for processing together, useful for repetitive operations.

Example:

data example;
    set original_data;
    array scores[5] score1-score5;
    do i = 1 to 5;
        scores[i] = scores[i] * 1.1;
    end;
run;

14. How do you create a report using PROC REPORT in SAS?

PROC REPORT creates detailed and customizable reports, summarizing data and computing statistics.

Example:

proc report data=sashelp.class nowd;
    column Name Age Height Weight;
    define Name / display 'Student Name';
    define Age / analysis mean 'Average Age';
    define Height / analysis mean 'Average Height';
    define Weight / analysis mean 'Average Weight';
run;

15. What is the purpose of the ODS statement in SAS?

The ODS statement manages and customizes output, directing it to different formats like HTML, PDF, and RTF.

Example:

ods html file='output.html';
proc print data=sashelp.class;
run;
ods html close;

16. Describe the use of the PROC FREQ procedure in SAS.

PROC FREQ generates frequency tables, counting occurrences of each unique value in a dataset.

Example:

proc freq data=sashelp.class;
    tables sex age;
run;

17. How do you perform a logistic regression in SAS?

Logistic regression models the relationship between a binary dependent variable and independent variables using PROC LOGISTIC.

Example:

proc logistic data=mydata;
    model target_variable(event='1') = predictor1 predictor2 predictor3;
run;

18. Explain the use of the PROC GLM procedure in SAS.

PROC GLM fits general linear models, handling analyses like regression, ANOVA, and MANOVA.

Example:

proc glm data=dataset;
    class factor;
    model response = factor;
    means factor / tukey;
run;
quit;

19. How do you create a custom format using PROC FORMAT in SAS?

Custom formats control data display, created using PROC FORMAT.

Example:

proc format;
    value agefmt
        low - 12 = 'Child'
        13 - 19 = 'Teenager'
        20 - 64 = 'Adult'
        65 - high = 'Senior';
run;

data people;
    input name $ age;
    datalines;
    John 10
    Jane 25
    Bob 70
    ;
run;

proc print data=people;
    format age agefmt.;
run;

20. Describe the use of the LAG function in SAS.

The LAG function accesses a variable’s value from a previous row, useful in time series analysis.

Example:

data example;
    input id value;
    lag_value = lag(value);
    datalines;
1 10
2 20
3 30
4 40
;
run;

proc print data=example;
run;

21. Explain the use of the PROC UNIVARIATE procedure in SAS.

PROC UNIVARIATE performs descriptive statistics and exploratory data analysis on continuous variables.

Example:

proc univariate data=sashelp.class;
   var height;
   histogram height / normal;
   inset mean std / position=ne;
run;

22. Describe how to perform data cleaning in SAS.

Data cleaning in SAS involves handling missing values, removing duplicates, correcting errors, and standardizing data formats.

• Handling Missing Values: Use PROC MEANS or PROC FREQ to identify missing values. Replace or impute missing values with IF and THEN statements.
• Removing Duplicates: Use PROC SORT with NODUPKEY to remove duplicates.
• Correcting Errors: Use IF and THEN statements to correct errors.
• Standardizing Data Formats: Use INPUT and PUT functions to convert data types and standardize formats.

Example:

data cleaned_data;
    set raw_data;
    if missing(variable) then variable = 0;
run;

proc sort data=cleaned_data nodupkey;
    by key_variable;
run;

data cleaned_data;
    set cleaned_data;
    if variable < 0 then variable = abs(variable);
run;

data cleaned_data;
    set cleaned_data;
    standardized_date = input(date_variable, yymmdd10.);
    format standardized_date yymmdd10.;
run;

23. What are the different types of joins available in SAS?

In SAS, joins combine data from multiple datasets based on a common variable. Types of joins include inner, left, right, full, and cross joins.

24. Explain the use of the PROC TABULATE procedure in SAS.

PROC TABULATE creates multi-dimensional tables summarizing data, handling summary statistics like means, sums, and counts.

Example:

proc tabulate data=sashelp.class;
    class sex;
    var age height weight;
    table sex, (age height weight)*(mean sum);
run;

25. How do you create and use user-defined functions in SAS?

User-defined functions in SAS are created using PROC FCMP, allowing custom functions for reuse.

Example:

proc fcmp outlib=work.funcs.myfuncs;
    function add_numbers(a, b);
        return (a + b);
    endsub;
run;

options cmplib=work.funcs;

data _null_;
    result = add_numbers(5, 10);
    put result=;
run;