An important step in creating confidence intervals for proportions is to check whether the success/failure conditions ha

[answerhappygod]

An important step in creating confidence intervals for
proportions is to check whether the success/failure conditions have
been met otherwise the interval created will not be valid (i.e. we
should not have created that interval)!
The following examples are estimating the proportion of
vegetarians in the population. Try to determine whether or not the
assumptions have been met.
In a sample of 25 people surveyed, 3 were vegetarians.
In a sample of 200 people surveyed, 15 were vegetarians.
In a sample of 90 people surveyed, 7 were vegetarians.
In a sample of 30 people surveyed, 4 were vegetarians.