Lab 0: Getting Started/Basic One-Sample Data Analysis & Inference

By default now, SPlus starts in the local drive of your machine, which means that everyone using that computer through the day will have the same _Data and _Prefs directory. Because of the potential to corrupt your work and output, you should create your own class directory as well as multiple working directories for each assignment.

1. Create a new folder in your z: drive. Call it: z:\env210
2. Create a folder for your current assignment. Get started with "lab0"
3. Download the data. Go to the assignment page, and right click on the dataset name. "Save Target As:" Save these data to your "lab0" folder.
4. Start Splus. Choose your default folder, which will be "env210".
5. Now go to "File" "Chapters" "Create Chapter". Choose the "lab0" directory, and make sure position is set to "1". This will store your Splus work (any variables you create, datasets and modifications to them) in this directory.

1. Using Splus, give mean, median, standard deviation and interquartile range for this dataset. Splus directions

2. Create 3 plots of the data: a boxplot, a histogram of counts and a frequency histogram. Label axes with units of measurement, and give titles to the graphs.
3. Calculate a 95% confidence interval for the mean concentration of soluable nitrogen using Splus. Note that you can use Splus to calculate quantiles and percentiles instead of the tables in the back of the book.

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   Additional practice exercises:
4. Calculate the above interval by hand and compare to the Splus solution.
5. Give a 1-sentence interpretation of what the interval in (b) means.

6. State any assumptions that are needed for inference about the above interval in (b) to be valid.

7. Two analysts perform separate hypothesis tests. (Assume unknown standard deviation as in (b).) Analyst 1 wants to know whether there is sufficient evidence to suggest that the mean differs from 1.69 mg/g. Analyst 2 evaluates the claim that the mean concentration is greater than 1.69 mg/g. For each analyst, write out the hypothesis test, giving null and alternative hypotheses, test statistics, and p-values. Are their conclusions the same or different? Why?