Unfortunately arsenic occurs naturally in some ground water A mean arsenic level of 8 0 parts per billion ppb is considered safe

Question

Unfortunately arsenic occurs naturally in some ground water A mean arsenic level of 8 0 parts per billion ppb is considered safe for agricultural use A well in Texas is used to water cotton crops This well is tested on a regular basis for arsenic A random sample of 41 tests gave a sample mean of x 7 1 ppb arsenic with s 2 2 ppb Does this information indicate that the mean level of arsenic in this well is less than 8 ppb Use 0 01 LUSE SALT a What is the level of significance 0 01 State the null and alternate hypotheses in parts per billion Enter for as needed Ho 8 H 8 b What sampling distribution will you use Explain the rationale for your choice of sampling distribution We ll use the standard normal since the sample size is large and is known We ll use the Student s t since the sample size is large and o is unknown We ll use the standard normal since the sample size is large and is unknown We ll use the Student s t since the sample size is large and o is known Compute the appropriate sampling distribution value of the sample test statistic Round your answer to two decimal places c Estimate the P value P value 0 100 0 050 P value 0 100 0 010 P value 0 050 0 005 P value 0 010 P value 0 005

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