Sewage and industrial pollutants dumped into a body of water can reduce the dissolved oxygen concentration and adversely affect aquatic species. In one study, weekly readings are taken from the same location in a  river over a two-month period.

Some scientists think that 5.0 ppm is a dissolved O₂ level that is marginal for fish to live. Conduct a statistical test to determine whether the mean dissolved O₂ concentration is less than 5.0 ppm at the 95% confidence level. State clearly the null and alternative hypotheses.

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Week Number Dissolved O2, ppm 1 4.9 5.1 3 5.6 4 4.3 4.7 4.9 7 4.5 8 5.1