You recently completed a study concerning the planned voting behaviour of Michigan residents by telephone. Your sample size was 300 and you found that 40% of the voters polled were voting for the candidate that you support, and 60% of the voters polled were voting for the other candidate. What is the 95% confidence interval concerning the proportion of voters voting for your preferred candidate?

To find the confidence interval for the proportion of voters voting for your preferred candidate, we can use the formula for the confidence interval of a proportion:

CI = \hat{p} \pm z \times \sqrt{\frac{\hat{p}(1-\hat{p})}{n}}

where:
- \hat{p} is the sample proportion (40% or 0.40),
- z is the z-score corresponding to the desired confidence level (95% confidence level corresponds to z = 1.96),
- n is the sample size (300).

Plugging in the values, we get:

CI = 0.40 \pm 1.96 \times \sqrt{\frac{0.40 \times 0.60}{300}}

Calculating this expression gives us the 95% confidence interval for the proportion of voters voting for your preferred candidate.

CI = 0.40 \pm 1.96 \times \sqrt{\frac{0.24}{300}}
CI = 0.40 \pm 1.96 \times \sqrt{0.0008}
CI = 0.40 \pm 1.96 \times 0.02828
CI=0.40\pm0.0554

So, the 95% confidence interval concerning the proportion of voters voting for your preferred candidate is \boxed{0.3446\text{ to }0.4554} .