Problem 12E
The article “Permeability, Diffusion and Solubility of Gases” (B. Flaconnéche, et al., Oil and Gas Science and Technology, 2001:262278) reported on a study of the effect of temperature and other factors on gas transport coefficients in semicrystalline polymers. The permeability coefficient (in 106 cm3 (STP) /cm • s • MPa) of CO2 was measured for extruded medium density polyethelene at both 60°C and 61°C. The results are as follows:
60ºC: 
54 
51 
61 
67 
57 
69 
60 

60 
63 
62 




61ºC 
58 
60 
66 
66 
68 
61 
60 
Find a 95% confidence interval for the difference in the permeability coefficent between 60°C and 61ºC.
Lecture 9: Estimating Proportions with Confidence 10.1: Overview of Confidence Intervals Confidence Intervals concept: Use sample data to estimate a population parameter Population (size N) = the whole group that we want to make conclusions on Parameter = summary about population Random sample of size n = a few units selected from population Statistic = summary about the sample Sample estimate = provides our best guess as to what is the value of the population parameter, but it is not 100% accurate. Concept: The value of the sample estimate will vary from one sample to the next. The values often vary around the population parameter and the standard