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