Question

Is your food safe? Do you feel confident or not confident that the food available at most grocery stores is safe to eat? when a gallup poll asked this question, $87\%$of the sample said they were confident." Callup announced the poll's margin of error for $95\%$confidence as$\pm 3$ percentage points. Which of the following sources of error are included in this margin of error? Explain.

(a) Gallup dialed landline telephone numbers at random and so missed all people without landline phones, including people whose only phone is a cell phone.

(b) Some people whose numbers were chosen never answered the phone in several calls or answered but refused to participate in the poll.

(c) There is chance variation in the random selection of telephone numbers.

Short answer

(a) This error will not be included in the margin of error

(b) This error will not be included in the margin of error

(c)This error will be included in the margin of error

Step-by-step solution

Part (a) Step 1:Given Information

Given in the question that,Gallup contacted landline phone numbers at random and so missed all respondents who don't have a landline phone, even those who only have a cell phone. we have to find such error is included in the margin of error.

Part (a) step2: explanation

This is an example of inadequate coverage. We know that undercover errors are not included in the margin of error. As a result, this error will be excluded from the margin of error.

Part (b) step 1: Given Information

Given In the question that, Some of the people whose numbers were chosen never answered the phone or answered but repeatedly declined to participate in the survey. We must determine whether or not such a mistake is included in the error margin.

Part (b) step 2: Explanation 

This is an example of a non-response case. We know that non-response mistakes are not included in the margin of error. As a result, this error will be excluded from the margin of error.

Part (C) Step-1: Given Information

Given in the question that there is some chance of fluctuation in the random selection of phone numbers we have to discover, that this inaccuracy is factored into the margin of error.

Part(C) Step 2: Explanation 

This error will be included in the margin of error because it is caused by sample variability.