Which concept determines the width of a confidence interval and is calculated using z-scores?

Which concept determines the width of a confidence interval and is calculated using z-scores?

• A. Margin of Error
• B. Confidence Level
• C. Degrees of Freedom
• D. Point Estimate

Answer: (A)

The width of a confidence interval is determined by the margin of error. The margin of error is the amount added to and subtracted from the point estimate to form the interval, and it is calculated as a z-score multiplier times the standard error. The z-score comes from the desired confidence level (for example, about 1.96 for a 95% interval) and is applied to the variability in the data. So, this margin of error controls how wide the interval will be. The confidence level influences which z value is used, but the actual width is set by the margin of error. Degrees of freedom would come into play if you used a t-distribution instead of z, and the point estimate is the center, not the width.

The width of a confidence interval is determined by the margin of error. The margin of error is the amount added to and subtracted from the point estimate to form the interval, and it is calculated as a z-score multiplier times the standard error. The z-score comes from the desired confidence level (for example, about 1.96 for a 95% interval) and is applied to the variability in the data. So, this margin of error controls how wide the interval will be. The confidence level influences which z value is used, but the actual width is set by the margin of error. Degrees of freedom would come into play if you used a t-distribution instead of z, and the point estimate is the center, not the width.