Final answer:
To create a 99 percent confidence interval for the proportion of American adults who download music weekly, use the formula: CI = p ± z * sqrt((p * (1-p)) / n). Factors that could affect the survey's outcome that are not covered by the margin of error include response bias, non-response bias, and sampling bias. Without performing any calculations, a decrease in the confidence level from 99% to 90% would result in a wider confidence interval.
Step-by-step explanation:
a. To create a 99 percent confidence interval for the proportion of American adults who download music weekly, we need to use the formula:
CI = p ± z * sqrt((p * (1-p)) / n)
Where CI is the confidence interval, p is the proportion of adults who download music weekly, z is the z-score corresponding to the desired confidence level, and n is the sample size. In this case, the sample size is 3383 and the proportion is 1464/3383. Using a z-score of 2.576 (corresponding to a 99% confidence level), the confidence interval is:
CI = (1464/3383) ± 2.576 * sqrt(((1464/3383) * (1-(1464/3383))) / 3383) = 0.428 ± 0.014
So, the 99% confidence interval for the population proportion is approximately 0.414 to 0.442.
b. Factors that could affect the survey's outcome that are not covered by the margin of error include response bias, non-response bias, and sampling bias.
c. Without performing any calculations, we can expect that a decrease in the confidence level from 99% to 90% would result in a wider confidence interval. This means that the range of values within which we can be confident the true population proportion lies would be larger with a 90% confidence level compared to a 99% confidence level.