A study was done to assess the ash content in peat moss used for textile fiber. High
ash content affects the quality of the textile. The following data are measurements of
the percentage of ash by weight:
(25+15+15= 55 Points)
0.5 1.8 4.0 1.0 2.0 1.1 1.6 2.3 3.5 2.2 2.0 3.8 3.0 2.3 1.8 3.6 2.4 0.8 3.4 1.4 1.9 2.3
1.2 1.9 2.3 2.6 3.1 2.5 1.7 5.0 1.3 3.0 2.7 1.2 1.5 3.2 2.4 2.5 1.9 3.1 2.4 2.8 2.7 4.5
2.1 1.5 0.7 3.7 1.8 1.7
(a) Construct a 95% confidence interval for the mean percentage of ash by weight.
Verify whether the underlying distributional assumption is satisfied or not. Give
adequate justifications in favor of your claim.
(b) At 5% level of significance, test whether the mean percentage of ash by weight is
significantly different from 2.75 or not. Comment on the accuracy of the decision
you take.
(c) Estimate the square root of the mean percentage of ash by weight by appropriate
estimator. Compute its standard error.
