The compressive strength of some material is being tested by an engineer.The data in the textfileProblem 2a.

Construct a 90% confidence interval on the mean strength of x4.

y x1 x2 x3 x4 x5 x6 8.0 5.2 19.6 29.6 94.9 2.1 2.3 8.3 5.2 19.8 32.4 89.7 2.1 1.8 8.5 5.8 19.6 31.0 96.2 2.0 2.0 8.8 6.4 19.4 32.4 95.6 2.2 2.1 9.0 5.8 18.6 28.6 86.5 2.0 1.8 9.3 5.2 18.8 30.6 84.5 2.1 2.1 9.3 5.6 20.4 32.4 88.8 2.2 1.9 9.5 6.0 19.0 32.6 85.7 2.1 1.9 9.8 5.2 20.8 32.2 93.6 2.3 2.1 10.0 5.8 19.9 31.8 86.0 2.1 1.8 10.3 6.4 18.0 32.6 87.1 2.0 1.6 10.5 6.0 20.6 33.4 93.1 2.1 2.1 10.8 6.2 20.2 31.8 83.4 2.2 2.1 11.0 6.2 20.2 32.4 94.5 2.1 1.9 11.3 6.2 19.2 31.4 83.4 1.9 1.8 11.5 5.6 17.0 33.2 85.2 2.1 2.1 11.8 6.0 19.8 35.4 84.1 2.0 1.8 12.3 5.8 18.8 34.0 86.9 2.1 1.8 12.5 5.6 18.6 34.2 83.0 1.9 2.0 

The Lower confidence limit=

Use 2decimal places

The upper confidence limit =