What does it mean to say we have 95% confidence in an interval computed

as m Å} 1.96(σm)?

Confidence intervals and English-language tests for international students (continued): Using the IELTS listening data presented in the previous exercise, practice evaluating data using confidence intervals.

A. Compute the 80% confidence interval.

B. How do the conclusion and the confidence interval change as we move from 95%  confidence to 80% confidence 

C. Why don't we talk about having 100% confidence? What would the confidence interval look like?

Suppose you compute a confidence interval with a sample size of 100. 

What will happen to the confidence interval if the sample size decreases to 80?

stay the same width 

decrease in width

increase in width

What is the z score for a confidence interval of 97.5% level of confidence?