Question 263:

Asked on July 6, 2008

Tags: Confidence Intervals , Critical Value , Margin of Error

1

Answer:

No answer provided yet.

For the first part of the question, you need to look up the area under the curve corresponding to 94%. Use the percentile to z-score calculator and enter .94 and be sure 2-sided is selected (since you're looking up Za/2 or the area in both tails). You should get 1.8817, which would be the critical value for a 94% Confidence Interval.

With the information provided in the second part of the question, you cannot compute a 90 or any sized confidence interval. All you have provided is the sample size, you'd need a mean, sd or proportion to compute a CI.

As your sample size increases your margin of error will decrease. See the article on the margin of error and confidence level.