The organisers of a conference wish to conduct a survey on 80 participants to gather feedback about their conference experience. The 800 participants who attended the conference come from various educational institutions, as shown in the table below:

1. Identify the appropriate sampling method and calculate the number of participants to sample from each stratum.

The appropriate method is stratified sampling, as the population is divided into distinct subgroups.
The proportion of the population to be sampled is $\frac{80}{800} = \frac{1}{10}$.
The number of participants to select from each educational institution is:

• Primary school: $350 \times \frac{1}{10} = 35$
• Secondary school: $250 \times \frac{1}{10} = 25$
• Junior college: $150 \times \frac{1}{10} = 15$
• Polytechnic: $50 \times \frac{1}{10} = 5$

2. Describe the random selection process within each stratum.

Within each of the 4 educational institution groups, assign a unique index to each participant. Then, use a random number generator to independently select the calculated number of unique participants from each group (i.e. by simple random sampling).

1. State an advantage of stratified sampling

Advantage: It ensures that the sample is representative of the population by maintaining the proportion of participants from each educational institution.

2. State a disadvantage of stratified sampling

Disadvantage: It is time-consuming and administrative-heavy, as it requires the population to be divided into distinct strata and a separate sampling frame to be compiled for each subgroup before randomly selecting from them.