Question

In a poll conducted by phone,

I. Some people refused to answer questions.

II. People without telephones could not be in the sample.

III. Some people never answered the phone in several calls.

Which of these possible sources of bias is included in the $\pm 2\%$margin of error announced for the poll?

a. I only

b. II only

c. III only

d. I, II, and III

e. None of these

Short answer

Option (e) "None of these" is correct.

Step-by-step solution

Given Information

It is given that:

I. Some people refused to answer questions.

II. People without telephones could not be in the sample.

III. Some people never answered the phone in several calls.

Explanation

Margin of Error has sampling errors only after data collection is done.

Option I is non response bias.

Option II is selection bias.

Option III is non response bias. These three are not sampling errors.

Hence, Option (e) is correct.