Arsenic occurs naturally in some ground water and can be toxic. A mean arsenic level of μ=9 parts per billion (ppb) is considered safe for agricultural use. A well in San Bernardino County is used to water strawberry crops. This well is tested on a regular basis for arsenic. A random sample of 42 tests gave a sample mean of 8.5 ppb arsenic, with a sample standard deviation of 2.1 ppb. Does this information indicate that the mean level of arsenic in this well is less than μ=9ppb? Use α=0.005 What is the level of significance? State the null and alternate hypotheses.
Arsenic occurs naturally in some ground water and can be toxic. A
What is the level of significance?
State the null and alternate hypotheses.
H0:H0:? σ p μ χ Select an answer < > = ≠ ppb
H1:H1:? μ p χ σ Select an answer > = ≠ < ppb
What is the value of the test statistic? (Round your answer to two decimal places.)
Find the P-value. (Round your answer to four decimal places.)
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