Use the sample information x¯x¯ = 43, ? = 6, n = 13 to calculate the following confidence intervals for ? assuming the sample is from a normal population.

(a) 90 percent confidence. (Round your answers to 4 decimal places.)
  
The 90% confidence interval is from  to

(b) 95 percent confidence. (Round your answers to 4 decimal places.)
  
The 95% confidence interval is from  to

(c) 99 percent confidence. (Round your answers to 4 decimal places.)
  
The 99% confidence interval is from  to

(d) Describe how the intervals change as you increase the confidence level.
  

• The interval gets narrower as the confidence level increases.

• The interval gets wider as the confidence level decreases.

• The interval gets wider as the confidence level increases.

• The interval stays the same as the confidence level increases