The most recent poll of 50 randomly-selected members of a school club with a total of 80 members showed that 38 are planning to vote for Talia as president of the club. Talia correctly determined that the margin of error, [tex]$E$[/tex], of the poll using a [tex]$95\%$[/tex] confidence interval ([tex]$z$[/tex]-score [tex]$1.96$[/tex]) is approximately [tex]$12\%$[/tex].

What is the [tex]$95\%$[/tex] confidence interval for the proportion of members planning to vote for Talia?

[tex]\[ C = \hat{p} \pm E \][/tex]

A. Between [tex]$26\%$[/tex] and [tex]$50\%$[/tex]
B. Between [tex]$38\%$[/tex] and [tex]$62\%$[/tex]
C. Between [tex]$51\%$[/tex] and [tex]$75\%$[/tex]
D. Between [tex]$64\%$[/tex] and [tex]$88\%$[/tex]



Answer :

To determine the 95% confidence interval for the proportion of club members planning to vote for Talia, we can outline the step-by-step process as follows:

1. Determine the sample proportion:
The sample proportion, denoted as [tex]\(\hat{p}\)[/tex], is calculated by dividing the number of members planning to vote for Talia by the total number of members surveyed.
[tex]\[ \hat{p} = \frac{38}{50} \][/tex]
2. Convert to decimal:
[tex]\[ \hat{p} = 0.76 \][/tex]

3. Margin of Error:
The margin of error [tex]\(E\)[/tex] is given as 12%, which in decimal form is:
[tex]\[ E = 0.12 \][/tex]

4. Calculate the confidence interval:
The confidence interval is calculated using the formula:
[tex]\[ C = \hat{p} \pm E \][/tex]
Substituting the values, we get:
[tex]\[ C = 0.76 \pm 0.12 \][/tex]

5. Find the lower bound:
[tex]\[ \text{Lower bound} = 0.76 - 0.12 = 0.64 \][/tex]

6. Find the upper bound:
[tex]\[ \text{Upper bound} = 0.76 + 0.12 = 0.88 \][/tex]

7. Convert to percentages:
To convert the decimal values into percentages, multiply by 100:
[tex]\[ \text{Lower bound percentage} = 0.64 \times 100 = 64\% \][/tex]
[tex]\[ \text{Upper bound percentage} = 0.88 \times 100 = 88\% \][/tex]

8. Conclusion:
The 95% confidence interval for the proportion of club members planning to vote for Talia is between 64% and 88%.

Thus, the correct answer is:
[tex]\[ \boxed{\text{between } 64 \% \text{ and } 88 \%} \][/tex]