Quiz

Select the best answer for each question. After completing the quiz, check your answers using the answer key in the appendix.
  1. Why can using an index reduce the number of I/O operations that are required for accessing a small subset?
    1. Using an index requires larger I/O memory buffers, which can hold more pages.
    2. The index does not have to be loaded into a memory buffer.
    3. The number of observations that SAS has to load into the program data vector (PDV) is decreased.
    4. The number of pages that SAS has to load into I/O buffers is decreased.
  2. You want to select a subset of observations in the data set Company.Products, and you have defined a simple index on the variable Rating. SAS cannot use the index to process which of the following WHERE statements? 
    1. where rating is missing;
    2. where rating=int(rating);
    3. where rating between 3.5 and 7.5;
    4. where rating=5.5;
  3. In which of the following situations is sequential access likely to be more efficient than direct access for WHERE processing?
    1. The subset contains more than 75% of the observations in the data set.
    2. The WHERE expression specifies both key variables in a single composite index.
    3. The data is sorted on the key variable.
    4. The data set is very large.
  4. You want to summarize data and group it by one variable. Which of the following tools could not be used?
    1. The DATA step with BY-group processing.
    2. The DATA step without BY-group processing.
    3. PROC SQL with a GROUP BY clause.
    4. PROC MEANS with a CLASS statement.
  5. Which of the following techniques does not summarize data for specific combinations of class variables?
    1. the NWAY option in multiple PROC MEANS steps.
    2. the TYPES statement in a PROC MEANS step.
    3. the WHERE= output data set option in a PROC MEANS step.
    4. a basic PROC MEANS step.
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