Given that:
---- i.e. the proportions that do not know their blood group
There are several sampling methods, however the best sampling method to use in this case is a simple random sampling.
This is because it gives each student in the campus an equal chance of being selected to participate.
The sample would be collected from the population of students in the school campus.
From the question, given proportion is about the students in the campus. So, the sample to be selected must represent the case study, which are the students
The chosen sample would be used by conducting a test of hypothesis
To carry out this test, we need to set the null and alternate hypotheses.
Then calculate the critical value.
Then the test statistic.
How the test statistic compares to the critical value will determine if the null hypothesis will be accepted or rejected
Further reading: