Question

A sample with a sample proportion of 0.4 and which of the following sizes will produce the widest 95% confidence interval when estimating the population parameter?
A. 100
B. 75
C. 50
D. 150

Answer 1

Answer:

C. 50

Step-by-step explanation:

In a sample with a number n of people surveyed with a probability of a success of $\pi$, and a confidence level of $1-\alpha$, we have the following confidence interval of proportions.

$\pi \pm z\sqrt{\frac{\pi(1-\pi)}{n}}$

In which

z is the zscore that has a pvalue of $1 - \frac{\alpha}{2}$.

The margin of error is:

$M = z\sqrt{\frac{\pi(1-\pi)}{n}}$

The higher the margin of error, the wider an interval is.

As the sample size increases, the margin of error decreases. If we want a widest possible interval, we should select the smallest possible confidence interval.

So the correct answer is:

C. 50