1) A random sample of 36 measurements was selected from a population with unknown mean and known standard deviation = 18. The sample mean is x = 12

a) Calculate a 95% confidence interval for mean.

b) Complete Problem (a), with a 99% confidence interval instead of a 95% confidence

interval.

2) The white wood material used for the roof of an ancient Japanese temple is imported from Northern Europe. The wooden roof must withstand as much as 100 centimetres of snow in the winter. Architects at Tohoku University (Japan) conducted a study to estimate the mean bending strength of the white wood roof. A sample of 25 pieces of the imported wood were tested and yielded the following statistics on breaking strength: x = 74.5, s = 10.9.

Estimate the true mean breaking strength of the white wood with a 90% confidence

interval.