How do you compute the mean of a numeric column in the LDS?

How do you compute the mean of a numeric column in the LDS?

• A. Divide the sum of all values by the total number of records, including missing.
• B. Sum all valid values and divide by the count of valid records.
• C. Take the maximum value.
• D. Count the records and divide the total by that count.

Answer: (B)

Mean is found by averaging the actual numbers present, so you sum all valid (non-missing) values and divide by how many valid values there are. If there are missing entries, they don’t contribute to the sum or to the count, so they’re ignored. That’s why the correct approach is to sum only valid values and divide by the count of valid records. The other options fail because including missing values in the divisor misdefines the average, taking the maximum is not averaging at all, and counting records and dividing by that count would either include missing values as zeros or otherwise misunderstand what you’re averaging.

Mean is found by averaging the actual numbers present, so you sum all valid (non-missing) values and divide by how many valid values there are. If there are missing entries, they don’t contribute to the sum or to the count, so they’re ignored. That’s why the correct approach is to sum only valid values and divide by the count of valid records.

The other options fail because including missing values in the divisor misdefines the average, taking the maximum is not averaging at all, and counting records and dividing by that count would either include missing values as zeros or otherwise misunderstand what you’re averaging.