Find the width of the 95 percent confidence interval for mean.
For a sample of 138 independent observations from a normal distribution of unknown μ and variance σ^{2} = 2.6, the sample mean is 52.3. What is the width of the 95 percent confidence interval for μ?
(i) 0.269
(ii) 0.538
(iii) 6.3208
(iv) 0.0116
(v) 0.0233