3. (5 points) Classify each sample as random, systematic, stratified, or cluster
(a) In a large school district, all teachers from two buildings are interviewed to determine
whether they believe the students have less homework to do now than in previous years.
(b) Which type of sampling is being employed if the country is divided into economic
classes and a sample is chosen from each class to be surveyed?
(c) Mail carriers of a large city are divided into four groups according to gender (male or
female) and according to whether they walk or ride on their routes. Then 10 are selected
from each group and interviewed to determine whether they have been bitten by a dog in
the last year.
(d) Every 200th hamburger manufactured is checked to determine its fat content.
(e) In a large school district, a researcher number all the full-time teachers and then
randomly selects 50 teachers to be interviewed.