Arsenic occurs naturally in some ground water and can be toxic. A mean arsenic level of=10parts 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 45 tests gave a sample mean of 10.6 ppb arsenic, with a sample standard deviation of 3.8 ppb. Does this information indicate that the mean level of arsenic in this well is more than=10ppb? Use=0.03

What is the level of significance?

State the null and alternate hypotheses.

H0:?

p

Select an answer

<

>

=

ppb

H1:?

p

Select an answer

<

>

=

ppb

What sampling distribution will you use? Explain the rationale for you choice of sampling distribution.

• The Student's t, since we have a simple random sample that is large andis known.
• The standard normal, since we have a simple random sample that is large andis known.
• The standard normal, since we have a simple random sample that is large.
• The Student's t, since we have a simple random sample that is large.

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.)

Based on your results, will you reject or fail to reject the null hypothesis? Are the data statistically significant at level?

• At the=0.03level, we fail to reject the null hypothesis and conclude the data are statistically significant.
• At the=0.03level, we reject the null hypothesis and conclude the data are statistically significant.
• At the=0.03level, we reject the null hypothesis and conclude the data are not statistically significant.
• At the=0.03level, we fail to reject the null hypothesis and conclude the data are not statistically significant.

Interpret your conclusion in the context of the application.

• There is sufficient evidence at the 0.03 level to conclude that the mean level of arsenic in the well is more than 10 ppb.
• There is insufficient evidence at the 0.03 level to conclude that the mean level of arsenic in the well is more than 10 ppb.