If the estimate of expected population proportion having a desired characteristic based on intuition is 60 percent, the acceptable error is plus or minus 5 percent, and the z-value for a 95 percent level of confidence is 1.96, the needed sample size is approximately:
A) 187.
B) 369.
C) 295.
D) 196.
E) 950.

Question

Quizplus · Accepted Answer

The needed sample size can be calculated using the formula for estimating a population proportion: $n = \frac{{Z^2 \times p(1-p)}}{{E^2}}$, where $Z$ is the z-value for the desired level of confidence (1.96 for 95%), $p$ is the estimated population proportion (0.60), and $E$ is the acceptable error (0.05). Plugging in the values: $n = \frac{{1.96^2 \times 0.60 \times (1-0.60)}}{{0.05^2}} \approx 369$.

If the Estimate of Expected Population Proportion Having a Desired