In the random sample of 46 bolts, the mean length was 1.28 inches and standard deviation was 0.07 inch. Employ a normal distribution or a t- distribution to develop a 99% confidence interval for the mean.
Which distribution must be employed to construct the 99% confidence interval ?
a. Employ a normal distribution because the lengths are normally distributed and σ is known.
b. Employ a t-distribution because n≥ 30.
c. Employ a t- distribution because the lengths are normally distributed and σ is known
d. Use a normal distribution because n≥ 30.
The 99% confidence interval is ......
(Type your answer in interval notation. Round to two decimal places as needed)