4. The strength of wood products used in construction is measured to be sure that they are suitable for the purpose for which they are used. Measurements, in megapascals, of the strength needed to break green mixed oak boards were made. The sample means, standard deviations, and sample sizes for four different grades of lumber are presented in the following table.
Grade Sample Mean Sample St. Dev. Sample Size
Select 45.1 8.52 32
No. 1 42.0 5.50 11
No. 2 33.2 6.71 15
Below grade 38.1 8.04 42
Can you conclude that the strength differs for different grades of lumber? Use a significance level of 0.05. Use SALT to calculate the test statistic and the P-value.
(a) State the hypothesis.
(b) State the test statistic. (Round to 2 decimal places)
(c) State the P-value. (Round to 4 decimal places)
(d) What is your decision?
(e) State a conclusion that is specifically related to this question.