All calculations should be completed only using R or RStudio. For each part, include a copy of your R code used and the output of your code. (i.e. Copy and paste the relevant pieces into a Word document (or other word processing document).)

Part 1 (5 points)

Include any used R code and the written up solutions to all parts below.

In a study of factors thought to be responsible for the adverse effects of smoking on human reproduction, cadmium level determinations (nanograms per gram) were made on placenta tissue of a random sample of 14 mothers who were smokers and an independent random sample of 18 non-smoking mothers. The results were as follows:

*Non-smokers: *

10.0 25.5 8.4 9.8 12.8 7.5 25.0 11.8 11.8 12.2 9.8 15.0 12.5 15.4 23.5 9.4 25.1 19.5

*Smokers: *

30.0 12.5 30.1 20.4 15.0 24.1 30.5 17.8 16.8 14.8 13.4 28.5 17.5 14.4

(a) Store the data for non-smokers in a vector called nonsmokers. We want to test the research hypothesis that the mean cadmium level for non-smoking mothers is less than 16 nanograms per gram. Copy and past the appropriate R command and output you would use to do test.

(b) Clearly state the p-value you found from part (a). Using the significance level =0.10, should we reject the null hypothesis?

(c) a sentence stating your conclusion of the hypothesis test you just performed. (i.e. Write conclusion in plain language so that a non-statistician could understand the conclusion of the test.)

(d) Store the data for smokers in a vector called smokers. Calculate a 95% confidence interval (i.e. a two-sided confidence interval) for the mean cadmium level of mothers who smoke. Copy and paste the appropriate R command and output you would use to create confidence interval. In an additional line, clearly state the values you get for the confidence interval from your output.

(e) Is it reasonable to conclude that the mean cadmium level of mothers who smoke is 23 nanograms per gram? Explain, using your confidence interval.