Is Chicago's water acceptable?

    The growth of organisms in water depends greatly on the of a body of water.  This important because pH is the measure of the H+ (hydrogen) ion concentration in the water.  Pure deionized water contains equal amounts of H+ and OH (hydroxide) ions.  The reason organisms are so sensitive to pH levels is that they have lived and adapted to water within a small range of pH levels.  Organisms are so sensitive to pH levels that they will not always survive if the pH level changes.  Extreme pH values can cause the death of organisms like young fish and insects which are sensitive to pH levels below 5.  Adult fish are very sensitive to pH levels above 8.5, the maximum normal range.  By collecting an amount of the water quality data from the Water Reclamation District of Greater Chicago, we determined that the quality of water is in the normal range (6.5-8.5).  If the water pH values are between these ranges, the water should be suitable for survival of most organisms.

    The Ranges of pH values go from 0 to 14.  The lower the pH value, the more acidic the substance is.  The higher the pH value, the more basic the substance is.

Part I.

The above bell-shaped graph shows that most of the pH levels surround the median of all of the pH levels in the sampled group and do so in a nearly symmetrical fashion.  The chart above also shows that 65% of the pH values fall between 7 and 8.5

Table #1: Summary Statistics for pH levels in general use waters

    The above table shows that the mean, or average is 7.8.  This is between the normal range for organisms to survive.(6.5-8.5)

Confidence Testing.

    Since the average of the sample might not have been the average of all of Chicago's water, a test was determined to see if one could be 95% confident that the pH values were acceptable for life.  It was determined that it was impossible to prove the assumption wrong that Chicago's pH levels were acceptable.