Data were collected on random specimens of tuna from 1991 and 2010. The mercury level for each fish specimen was recorded. For the sample of 43 specimens of Albacore tuna, the average mercury level was found to be 0.358 parts per million (ppm) and the standard deviation of mercury level to be 0.138 ppm. The data are not strongly skewed.
a. Identify the observational unit for this study.
b. Identify the variable of interest and whether it is categorical or quantitative.
c. In the context of this study, explain why it is valid to use the theory-based (t-distribution) approach to find a confidence interval?
d. Use the Theory-Based Inference applet to find and report a 95% confidence interval for the parameter of interest. Also, interpret the interval in the context of the study.