SAS interview questions

Very Basic

· What SAS statements would you code to read an external raw data file to a DATA step?

· How do you read in the variables that you need?

· Are you familiar with special input delimiters? How are they used?

· If reading a variable length file with fixed input, how would you prevent SAS from reading the next record if the last variable didn't have a value?

· What is the difference between an informat and a format? Name three informats or formats.

· Name and describe three SAS functions that you have used, if any?

· How would you code the criteria to restrict the output to be produced?

· What is the purpose of the trailing @? The @@? How would you use them?

· Under what circumstances would you code a SELECT construct instead of IF statements?

· What statement do you code to tell SAS that it is to write to an external file? What statement do you code to write the record to the file?

· If reading an external file to produce an external file, what is the shortcut to write that record without coding every single variable on the record?

· If you're not wanting any SAS output from a data step, how would you code the data statement to prevent SAS from producing a set?

· What is the one statement to set the criteria of data that can be coded in any step?

· Have you ever linked SAS code? If so, describe the link and any required statements used to either process the code or the step itself.

· How would you include common or reuse code to be processed along with your statements?

· When looking for data contained in a character string of 150 bytes, which function is the best to locate that data: scan, index, or indexc?

· If you have a data set that contains 100 variables, but you need only five of those, what is the code to force SAS to use only those variable?

· Code a PROC SORT on a data set containing State, District and County as the primary variables, along with several numeric variables.

· How would you delete duplicate observations?

· How would you delete observations with duplicate keys?

· How would you code a merge that will keep only the observations that have matches from both sets.

· How would you code a merge that will write the matches of both to one data set, the non-matches from the left-most data set to a second data set, and the non-matches of the right-most data set to a third data set.

Base SAS

· What is the effect of the OPTIONS statement ERRORS=1?

· What's the difference between VAR A1 - A4 and VAR A1 -- A4?

· What do the SAS log messages "numeric values have been converted to character" mean? What are the implications?

· Why is a STOP statement needed for the POINT= option on a SET statement?

· How do you control the number of observations and/or variables read or written?

· Approximately what date is represented by the SAS date value of 730?

· How would you remove a format that has been permanently associated with a variable??

· What does the RUN statement do?

· Why is SAS considered self-documenting?

· What areas of SAS are you most interested in?

· Briefly describe 5 ways to do a "table lookup" in SAS.

· What versions of SAS have you used (on which platforms)?

· What are some good SAS programming practices for processing very large data sets?

· What are some problems you might encounter in processing missing values? *In Data steps? Arithmetic? Comparisons? Functions? Classifying data?

· How would you create a data set with 1 observation and 30 variables from a data set with 30 observations and 1 variable?

· What is the different between functions and PROCs that calculate the same simple descriptive statistics?

· If you were told to create many records from one record, show how you would do this using arrays and with PROC TRANSPOSE?

· What are _numeric_ and _character_ and what do they do?

· How would you create multiple observations from a single observation?

· For what purpose would you use the RETAIN statement?

· What is a method for assigning first.VAR and last.VAR to the BY group variable on unsorted data?

· What is the order of application for output data set options, input data set options and SAS statements?

· What is the order of evaluation of the comparison operators: + - * / ** ( ) ?

Testing, debugging

· How could you generate test data with no input data?

· How do you debug and test your SAS programs?

· What can you learn from the SAS log when debugging?

· What is the purpose of _error_?

· How can you put a "trace" in your program?

· Are you sensitive to code walk-throughs, peer review, or QC review?

· Have you ever used the SAS Debugger?

· What other SAS features do you use for error trapping and data validation?

Missing values

· How does SAS handle missing values in: assignment statements, functions, a merge, an update, sort order, formats, PROCs?

· How many missing values are available? When might you use them?

· How do you test for missing values?

· How are numeric and character missing values represented internally?

General

· What has been your most common programming mistake?

· What is your favorite programming language and why?

· What is your favorite operating system? Why?

· Do you observe any coding standards? What is your opinion of them?

· What percent of your program code is usually original and what percent copied and modified?

· Have you ever had to follow SOPs or programming guidelines?

· Which is worse: not testing your programs or not commenting your programs?

· Name several ways to achieve efficiency in your program. Explain trade-offs.

· What other SAS products have you used and consider yourself proficient in using?

Functions

· How do you make use of functions?

· When looking for contained in a character string of 150 bytes, which function is the best to locate that data: scan, index, or indexc?

· What is the significance of the 'OF' in X=SUM(OF a1-a4, a6, a9);?

· What do the PUT and INPUT functions do?

· Which date function advances a date, time or date/time value by a given interval?

· What do the MOD and INT function do?

· How might you use MOD and INT on numerics to mimic SUBSTR on character strings?

· In ARRAY processing, what does the DIM function do?

· How would you determine the number of missing or nonmissing values in computations?

· What is the difference between: x=a+b+c+d; and x=SUM(a,b,c,d);?

· There is a field containing a date. It needs to be displayed in the format "ddmonyy" if it's before 1975, "dd mon ccyy" if it's after 1985, and as 'Disco Years' if it's between 1975 and 1985. How would you accomplish this in data step code? Using only PROC FORMAT.

· In the following DATA step, what is needed for 'fraction' to print to the log? data _null_; x=1/3; if x=.3333 then put 'fraction'; run;

· What is the difference between calculating the 'mean' using the mean function and PROC MEANS?

PROCs

· Have you ever used "Proc Merge"? (be prepared for surprising answers..)

· If you were given several SAS data sets you were unfamiliar with, how would you find out the variable names and formats of each dataset?

· What SAS PROCs have you used and consider yourself proficient in using?

· How would you keep SAS from overlaying the a SAS set with its sorted version?

· In PROC PRINT, can you print only variables that begin with the letter "A"?

· What are some differences between PROC SUMMARY and PROC MEANS?

· PROC FREQ:

*Code the tables statement for a single-level (most common) frequency.

*Code the tables statement to produce a multi-level frequency.

*Name the option to produce a frequency line items rather that a table.

*Produce output from a frequency. Restrict the printing of the table.

· PROC MEANS:

*Code a PROC MEANS that shows both summed and averaged output of the data.

*Code the option that will allow MEANS to include missing numeric data to be included in the report.

*Code the MEANS to produce output to be used later.

· Do you use PROC REPORT or PROC TABULATE? Which do you prefer? Explain.

Merging/Updating

· What happens in a one-on-one merge? When would you use one?

· How would you combine 3 or more tables with different structures?

· What is a problem with merging two data sets that have variables with the same name but different data?

· When would you choose to MERGE two data sets together and when would you SET two data sets?

· Which data set is the controlling data set in the MERGE statement?

· How do the IN= variables improve the capability of a MERGE?

· Explain the message 'MERGE HAS ONE OR MORE DATASETS WITH REPEATS OF BY VARIABLES".

Simple statistics

· How would you generate 1000 observations from a normal distribution with a mean of 50 and standard deviation of 20. How would you use PROC CHART to look at the distribution? Describe the shape of the distribution.

· How do you generate random samples?

Customized Report Writing

· What is the purpose of the statement DATA _NULL_ ;?

· What is the pound sign used for in the DATA _NULL_?

· What would you use the trailing @ sign for?

· For what purpose(s) would you use the RETURN statement?

· How would you determine how far down on a page you have printed in order to print out footnotes?

· What is the purpose of using the N=PS option?

Macro

· What system options would you use to help debug a macro?

· Describe how you would create a macro variable.

· How do you identify a macro variable?

· How do you define the end of a macro?

· How do you assign a macro variable to a SAS variable?

· For what purposes have you used SAS macros?

· What is the difference between %LOCAL and %GLOBAL?

· How long can a macro variable be? A token?

· If you use a SYMPUT in a DATA step, when and where can you use the macro variable?

· What do you code to create a macro? End one?

· Describe how you would pass data to a macro.

· You have five data sets that need to be processed identically; how would you simplify that processing with a macro?

· How would you code a macro statement to produce information on the SAS log? This statement can be coded anywhere.

· How do you add a number to a macro variable?

· If you need the value of a variable rather than the variable itself, what would you use to load the value to a macro variable?

· Can you execute a macro within a macro? Describe.

· Can you a macro within another macro? If so, how would SAS know where the current macro ended and the new one began?

· How are parameters passed to a macro?

Pharmaceutical Industry

· Describe the types of SAS programming tasks that you performed: Tables? Listings? Graphics? Ad hoc reports? Other?

· Have you been involved in editing the data or writing data queries?

· What techniques and/or PROCs do you use for tables?

· Do you prefer PROC REPORT or PROC TABULATE? Why?

· Are you involved in writing the inferential analysis plan? Tables specifications?

· What do you feel about hardcoding?

· How experienced are you with customized reporting and use of DATA _NULL_ features?

· How do you write a test plan?

· What is the difference between verification and validation?

Open-ended questions

· Describe a time when you were really stuck on a problem and how you solved it.

· Describe the function and utility of the most difficult SAS macro that you have written.

· Give me an example of ..

· Tell me how you dealt with ...

· How do handle working under pressure?

· Of all your work, where have you been the most successful?

· What are the best/worst aspects of your current job?

· If you could design your ideal job, what would it look like?

· How necessary is it to be creative in your work?

· If money were no object, what would you like to do?

· What would you change about your job?