12. Categorize each technique as simple random sample,
stratified sample, systematic sample, cluster sample, or convenient
sample.

a) To conduct a pre-election opinion poll on a proposed
amendment to the state constitution, a random sample of 10
telephone prefixes (first three digits of the phone number) was
selected, and all households from the phone prefixes selected were
called. ___________________________

b) To conduct a study on depression among the elderly, a sample
of 30 patients in a nearby nursing home was used.
______________________________________________.

c) To maintain quality control in a brewery, every
20^th bottle of beer coming off the production line was
opened and tested. __________________________________________.

d) To judge the appeal of a proposed television sitcom, a random
sample of 10 people from each of the three different age categories
was selected and those chosen were asked to rate a pilot show.
_________________________________________________

e) 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.

_____________________________________________________