A sample of 77 individuals working at a specific construction site office was chosen at random. The noise level (dBA) experienced by each individual was determined. The site manager is curious if there is evidence that average noise level experienced by all workers is less than 70 dBA. Perform an analysis. Use a significance level of 0.05. Use the provided R code under the Instructions, Data Sets and Code tab to obtain descriptive statistics, graphical displays and p-values.
a. Include a plot of the data.
b. Is there visual evidence that the true mean is less than 70 dBA? Explain. Must include context.
c. State the null and alternative hypothesis to answer the manager's question of interest.
d. Calculate the test statistic by hand and obtain a p-value by table. Show work.
e. Calculate the 95% Confidence Interval by hand. Show work.
f. Obtain a p-value from t test and confidence interval using R. Are your answers different than d and e?
g. Using the R output (from f) give a four part conclusion (shown in notes) and thoroughly answer the site managers question of interest. Must include context.
h. Optional. Append Code to the end of your document.