(a) For those wells with detectible levels of MTBE, construct a histogram for the MTBE values. From the histogram, estimate the proportion of contaminated wells with MTBE values that exceed 5 micrograms per liter.
(b) Find the mean and standard deviation for the pH levels of the sampled wells, and construct the interval y¯ ± 2s. Estimate the percentage of wells with pH levels that fall within the interval. What rule did you apply to obtain the estimate? Explain.
(c) Find the mean and standard deviation for the MTBE levels of the sampled wells and construct the interval y¯ ± 2s. Estimate the percentage of wells with MTBE levels that fall within the interval. What rule did you apply to obtain the estimate? Explain.
Dental Anxiety Scale. Psychology students at Wittenberg University completed the Dental Anxiety