1. State the preparation of the sampling frame and calculate the sampling interval.

Obtain a list of all the households in the housing estate and number them sequentially. Since a $10\%$ sample is required, the sampling interval is $k = \frac{100}{10} = 10$.

2. Explain the random starting point and the systematic selection of subsequent units.

Randomly select a starting number $r$ between $1$ and $10$ inclusive. Select the household numbered $r$, and then select every $10$th household thereafter (i.e., households numbered $r+10, r+20, \dots$) until $10\%$ of the households are chosen.

1. Describe an alternative method of sampling that fits the context.

Method: Stratified Sampling
Divide the households in the estate into mutually exclusive strata based on their flat type (e.g., 3-room, 4-room, 5-room). Within each stratum, randomly select 10% of the households using simple random sampling to form the final sample.

(Note: Simple Random Sampling is also an acceptable alternative method.)

2. State one advantage of this method over systematic sampling.

Advantage:
Stratified sampling ensures that every flat type (and thus demographic group) is proportionally represented in the sample. Systematic sampling might under-represent or over-represent certain flat types, especially if the sampling interval coincides with a periodic, structural pattern in the list of households (e.g., always picking corner units).