A process for producing vinyl floor covering has been stable for a long period of

time, and the surface hardness measurement of the flooring produced has a normal

distribution with mean 3.9 and standard deviation σ = 1.5. A second shift has been

hired and trained and their production needs to be monitored. Consider testing the

hypothesis

Scientists need to be able to detect small amounts of contaminants in the environment. As a check on current capabilities, measurements of lead content( μ g / L) are

taken from twelve water specimens spiked with a known concentration. (courtesy

of Paul Berthouex). 

2.4 2.9 2.7 2.6 2.9 2.0 2.8 2.2 2.4 2.4 2.0 2.5

The data has  and . Calculate the test statistic correct to two decimal places.