Unfortunately, arsenic occurs naturally in some ground water.t A mean arsenic level of u= 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 36 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 a = 0.01. A USE SALT (a) What is the level of significance? State the null and alternate hypotheses. O Ho: H= 8 ppb; H,:> 8 ppb O Ho: u< 8 ppb; H,: - 8 ppb O Ho: H= 8 ppb; H,:H < 8 ppb HoiH = 8 ppb; H,: u + 8 ppb O Ho: H > 8 ppb; H,: = 8 ppb (b) What sampling distribution will you use? Explain the rationale for your choice of sampling distribution. The standard normal, since the sample size is large and a is unknown. The Student's t, since the sample size is large and a is known. O The standard normal, since the sample size is large and a is known. The Student's t, since the sample size is large and a is unknown. What is the value of the sample test statistic? (Round your answer to three decimal places.) (c) Estimate the P-value. O P-value > 0.100 O 0.050 < P-value < 0.100 O 0.010 < P-value < 0.050 O 0.005 < P-value < 0.010 O P-value < 0.005 Sketch the sampling distribution and show the area corresponding to the P-value. -4 -2 -2 A plot of the Student's t-probability curve has a horizontal axis with values from -4 to 4. The curve enters the window from the left, just above the horizontal axis, goes up and to the right, changes direction over approximately o on the horizontal axis, and then goes down and to the right before exiting the window just above the horizontal axis. The area under the curve between DO-2.45 and 4 is shaded. (d) Based on your answers in parts (a) to (c), will you reject or fail to reject the null hypothesis? Are the data statistically significant at level a? O At the a = 0.01 level, we reject the null hypothesis and conclude the data are statistically significant. At the a = 0.01 level, we reject the null hypothesis and conclude the data are not statistically significant. O At the a = 0.01 level, we fail to reject the null hypothesis and conclude the data are statistically significant. O At the a = 0.01 level, we fail to reject the null hypothesis and conclude the data are not statistically significant. (e) Interpret your conclusion in the context of the application. O There is sufficient evidence at the 0.01 level to conclude that the mean level of arsenic in the well is less than 8 ppb. O There is insufficient evidence at the 0.01 level to conclude that the mean level of arsenic in the well is less than 8 ppb.

Glencoe Algebra 1, Student Edition, 9780079039897, 0079039898, 2018
18th Edition
ISBN:9780079039897
Author:Carter
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Chapter10: Statistics
Section10.5: Comparing Sets Of Data
Problem 13PPS
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Unfortunately, arsenic occurs naturally in some ground water.t A mean arsenic level of u = 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 36 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 a = 0.01.
A USE SALT
(a) What is the level of significance?
State the null and alternate hypotheses.
O Họ: u = 8 ppb; H,: u > 8 ppb
O Ho: H< 8 ppb; H: u = 8 ppb
O Ho: H = 8 ppb; H,: u < 8 ppb
O Ho: H= 8 ppb; H: u+ 8 ppb
HoiH> 8 ppb; H,: u = 8 ppb
(b) What sampling distribution will you use? Explain the rationale for your choice of sampling distribution.
The standard normal, since the sample size is large and a is unknown.
O The Student's t, since the sample size is large and a is known.
O The standard normal, since the sample size is large and a is known.
The Student's t, since the sample size is large and a is unknown.
What is the value of the sample test statistic? (Round your answer to three decimal places.)
(c) Estimate the P-value.
O P-value > 0.100
O 0.050 < P-value < 0.100
O 0.010 < P-value < 0.050
O 0.005 < P-value < 0.010
O
P-value < 0.005
Sketch the sampling distribution and show the area corresponding to the P-value.
-4
-2
A plot of the Student's t-probability curve has a horizontal axis
with values from -4 to 4. The curve enters the window from the
left, just above the horizontal axis, goes up and to the right,
changes direction over approximately o on the horizontal axis, and
then goes down and to the right before exiting the window just
above the horizontal axis. The area under the curve between
DO-2.45 and 4 is shaded.
(d) Based on your answers in parts (a) to (c), will you reject or fail to reject the null hypothesis? Are the data statistically
significant at level a?
O At the a = 0.01 level, we reject the null hypothesis and conclude the data are statistically significant.
O At the a = 0.01 level, we reject the null hypothesis and conclude the data are not statistically significant.
O At the a = 0.01 level, we fail to reject the null hypothesis and conclude the data are statistically significant.
O At the a = 0.01 level, we fail to reject the null hypothesis and conclude the data are not statistically significant.
(e) Interpret your conclusion in the context of the application.
O There is sufficient evidence at the 0.01 level to conclude that the mean level of arsenic in the well is less than 8 ppb.
O
There is insufficient evidence at the 0.01 level to conclude that the mean level of arsenic in the well is less than
8 ppb.
Transcribed Image Text:Unfortunately, arsenic occurs naturally in some ground water.t A mean arsenic level of u = 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 36 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 a = 0.01. A USE SALT (a) What is the level of significance? State the null and alternate hypotheses. O Họ: u = 8 ppb; H,: u > 8 ppb O Ho: H< 8 ppb; H: u = 8 ppb O Ho: H = 8 ppb; H,: u < 8 ppb O Ho: H= 8 ppb; H: u+ 8 ppb HoiH> 8 ppb; H,: u = 8 ppb (b) What sampling distribution will you use? Explain the rationale for your choice of sampling distribution. The standard normal, since the sample size is large and a is unknown. O The Student's t, since the sample size is large and a is known. O The standard normal, since the sample size is large and a is known. The Student's t, since the sample size is large and a is unknown. What is the value of the sample test statistic? (Round your answer to three decimal places.) (c) Estimate the P-value. O P-value > 0.100 O 0.050 < P-value < 0.100 O 0.010 < P-value < 0.050 O 0.005 < P-value < 0.010 O P-value < 0.005 Sketch the sampling distribution and show the area corresponding to the P-value. -4 -2 A plot of the Student's t-probability curve has a horizontal axis with values from -4 to 4. The curve enters the window from the left, just above the horizontal axis, goes up and to the right, changes direction over approximately o on the horizontal axis, and then goes down and to the right before exiting the window just above the horizontal axis. The area under the curve between DO-2.45 and 4 is shaded. (d) Based on your answers in parts (a) to (c), will you reject or fail to reject the null hypothesis? Are the data statistically significant at level a? O At the a = 0.01 level, we reject the null hypothesis and conclude the data are statistically significant. O At the a = 0.01 level, we reject the null hypothesis and conclude the data are not statistically significant. O At the a = 0.01 level, we fail to reject the null hypothesis and conclude the data are statistically significant. O At the a = 0.01 level, we fail to reject the null hypothesis and conclude the data are not statistically significant. (e) Interpret your conclusion in the context of the application. O There is sufficient evidence at the 0.01 level to conclude that the mean level of arsenic in the well is less than 8 ppb. O There is insufficient evidence at the 0.01 level to conclude that the mean level of arsenic in the well is less than 8 ppb.
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