Select the best answer
for each question. After completing the quiz, check your answers using
the answer key in the appendix.
-
Placing the subsetting
IF statement at the top rather than near the bottom of a DATA step
results in a savings in CPU usage. What happens if the subset is large
rather than small?
-
The savings in CPU usage
increases as the subset grows larger because the
I/O increases.
-
The savings in CPU usage
decreases as the subset grows larger. However, placing the subsetting
IF statement at the top of a DATA step always uses fewer resources
than placing it at the bottom.
-
The savings in CPU usage
remains constant as the subset grows larger. However, placing the
subsetting IF statement near the bottom of a data set is preferable.
-
The savings in CPU usage
decreases as the subset grows larger. However, placing the subsetting
IF statement near the bottom of a data set increases the
I/O.
-
Which of the following
statements is true about techniques that are used for modifying data
and attributes?
-
You can use PROC DATASETS
to modify both data values and variable attributes.
-
You can use PROC DATASETS
to modify only data values.
-
You can use the DATA
step to modify both data values and variable attributes.
-
You can use the DATA
step to modify only variable attributes.
-
For selecting observations,
is a subsetting IF statement or a WHERE statement more efficient?
Why?
-
A subsetting IF statement
is more efficient because it loads all observations sequentially into
the program data vector.
-
A subsetting IF statement
is more efficient because it examines what is in the input buffer
and selects observations before they are loaded into the program data
vector, which results in a savings in CPU operations.
-
A WHERE statement is
more efficient because it loads all observations sequentially into
the program data vector.
-
A WHERE statement is
more efficient because it examines what is in the input page buffer
and selects observations before they are loaded into the program data
vector, which results in a savings in CPU operations.
-
When is it more advantageous
to create a temporary SAS data set rather than a permanent SAS data
set?
-
When the external file
on which the data set is based might change between SAS sessions.
-
When the external file
on which the data set is based does not change between SAS sessions.
-
When the data set is
needed for more than one SAS session.
-
When you are converting
raw numeric values to SAS data values.
-
When you compare the
technique of using multiple DATASETS procedures to using a single
DATASETS procedure to modify the descriptor portion of a data set,
which is true?
-
A one-step DATASETS
procedure results in an increase in
I/O operations.
-
Multiple DATASETS procedures
result in a decrease in
I/O operations.
-
A one-step DATASETS
procedure results in a decrease in CPU usage.
-
Multiple DATASETS procedures
result in a decrease in CPU usage.
