Step 1: Alternate explanation via data source:
Sex ratio is computed from Census headcount data, which separately records the male and female population of an area.
Step 2: Apply the formula:
\[ \text{Sex Ratio} = \dfrac{\text{Female population} }{\text{Male population}} \times 1000 \] using the Census-recorded totals for that region.
Step 3: Final Answer:
It is the ratio of females to males, standardised per 1000 males, calculated directly from Census population counts.