The code block shown below contains an error. The code block is intended to return a new DataFrame with the mean of column sqft from DataFrame storesDF in column sqftMean. Identify the error. Code blo

Question

Options

• AThe argument to the mean() operation should be a Column abject rather than a string column
• BThe argument to the mean() operation should not be quoted.
• CThe mean() operation is not a standalone function - it's a method of the Column object.
• DThe agg() operation is not appropriate here - the withColumn() operation should be used instead.
• EThe only way to compute a mean of a column is with the mean() method from a DataFrame.2

• A
  11% (4)
• B
  3% (1)
• D
  6% (2)
• E
  81% (29)

Explanation

The code storesDF.agg(mean("sqft").alias("sqftMean")) references mean as a standalone function, which requires an explicit import from pyspark.sql.functions. Without that import, a NameError is raised at runtime. The exam identifies E as the error, pointing out that computing a mean requires the proper PySpark function API - either by importing mean from pyspark.sql.functions or by using the equivalent aggregation dictionary syntax storesDF.agg({"sqft": "mean"}). The other options describe non-issues: mean() does accept a string column name (ruling out A/B), it is a standalone function not a Column method (ruling out C), and agg() is appropriate for aggregations (ruling out D).

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