Blood pressure is being used to explain survival. It appears that high blood pressure is associated with a higher death rate. Since this is more than 10 times the sample size our s.d. formula is appropriate. Since both of these are larger than 10 it is reasonable to use the normal approximation.
Young people are less likely to vote than older people.
This is not a simple random sample because every group of 78 statisticians does not have an equal chance of being selected.