Answer:
Step-by-step explanation:
Hello!
The list of individuals from which a sample is selected is called the sampling frame. Ideally, the frame should list every individual in the population, but in practice, this is often difficult.
A-frame that leaves out part of the population is a common source of under coverage.
Step 1: Suppose that a sample of households in a community is selected at random from the telephone directory.
What households are omitted from this frame?
a. Households that do not answer the phone.
b. Households with unlisted numbers or without telephones.
c. Households that refuse to take part in surveys.d. Households with more than one telephone line.
b and c: If the sampling of households is done by choosing random telephone numbers from the directory, then the ones that are to be omitted are those households without a phone number and those that do not have their number listed in the directory.
Step 2: What types of people do you think are likely to live in these households? These people will probably be underrepresented in the sample.
1.People with extra time on their hands.
2. People without the extra income to keep a phone line will largely comprise the population without a phone line.
3. Very busy people or those interested in maintaining privacy will largely comprise those with unlisted numbers.
4. People who do not like to take surveys are likely to live in these households.
2 and 3: More than underrepresented they will be not represented at all. Since their numbers are not in the directory, they have zero probability of being picked for the sample.
Step 3: It is usual in telephone surveys to use random digit dialing equipment that selects the last four digits of a telephone number at random after being given the exchange (the first three digits). Which of the households underrepresented in the sample will be included in the sampling frame by random digit dialing?
a. all will be included.
b. Those people who do not have phones will be included (in some percentage), while those with unlisted numbers will not be included at all.
c. none will be included.
d. Those with unlisted numbers will be included (in some percentage), while those people who do not have phones will not be included at all
d. Those that don't have a phone number will not be included. If the sampling is done by random digit dialing, then even if their numbers are nor listed in the directory, there is a small probability that the random dialer will choose their numbers.
If the sampling was made manually, using only the phone listed in the directory then, logically, all households without a listed phone number will be excluded.
I hope it helps!
