Question

Out of 400 people sampled, 360 preferred Candidate A. Based on this, estimate what proportion of the voting population (π) prefers Candidate A. Use a 90% confidence level, and give your answers as decimals, to three places.

Answer 1

We need to construct the 90% confidence interval for the population proportion. We have been provided with the following information about the number of favorable cases:

Favorable Cases X =	360
Sample Size N =	400

The sample proportion is computed as follows, based on the sample size N=400 and the number of favorable cases X = 360:

The critical value for α=0.1 is . The corresponding confidence interval is computed as shown below:

Therefore, based on the data provided, 90% confidence interval for the population proportion is 0.875<p<0.925

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