1. A city is conducting a water quality study. It is measuring trace levels of a certain substance in the blood of residents who live in a city with unknown water quality against the same substance in another city with water quality that is known to be high. The blood levels of the substance in micrograms per milliliter are shown in the chart.

Known Quality	9	5	4	7	5	8	7	3	4	6	8	5
Unknown Quality	2	4	8	5	9	7	9	5	4	10	5	2

a. State the null hypothesis for the experiment.

b. Compare the results for the control group and the treatment group. Do you think that the researcher has enough evidence to reject the null hypothesis?

1. A researcher is investigating the health of some plants that have been treated with a chemical to increase their rate of growth. The table below shows the nitrogen levels of the treated and untreated plants in parts per million.

Untreated Plants	140	100	120	110	130	100	130	150	120
Treated Plants	120	180	130	150	220	150	170	160	130

a. State the null hypothesis about nitrogen for the experiment.

b. Compare the results for the control group and the treatment group. Do you think that the researcher has enough evidence to reject the null hypothesis?

1. A pharmaceutical company has developed a new drug to treat high blood pressure. Blood pressure measures are given as two distinct numbers, known as the systolic and diastolic pressures, both measured in milliliters of mercury (mm HG). The company claims that the drug will decrease systolic pressure to an average of 80 mm HG.

An independent trial is conducted by treating a random sample of 20 people with the drug. The findings are presented in the chart.

Company's Claims	Avg. Systolic 120 mm Hg	Avg. diastolic 80 mm Hg
Trial Results	Avg. 122 mm Hg	Avg. 85 mm Hg
Standard Deviation	10 mm Hg	2 mm Hg

a. Find the z-scores for both the systolic and diastolic trial results, rounded to the nearest hundredth.

b. Should the company's claims in regards to systolic pressure be rejected?

c. Should the company's claims in regards to diastolic pressure be rejected

1. A math teacher claimed that the average grade of the students in her Algebra 2 classes this year would be equal to the average grade of the same students in Algebra 1 classes two years ago. The average grade of Algebra 1 students two years ago was 92%. In a random sample of 25 current Algebra 2 students, the average grade was 87%, with a standard deviation of 7%.

a. Find the z-value, rounded to the nearest hundredth.

b. Is there enough evidence to reject the teacher's claim?