Question

After converting the nitrate into a purple dye, and measuring the absorbance of the purple dye on a spectrophotometer, a standard curve is used to convert the absorbance into concentration.

To make a standard curve, samples with known concentrations of
NO_{3}^{-} are run on the spectrophotemeter. The
samples with known concentrations are called standards. A linear
regression is then performed to relate the concentration of
NO_{3}^{-} to measured absorbance
values.

Here is a link to a spreadsheet containing a simulated data set.
There are standards and their related absorbance values, and there
are samples from two sites that were diluted, prior to processing
and measuring their absorbances. The groundwater originates from
the upslope site, and the hope is that the microbes in the soil are
removing the NO_{3}^{-} from the groundwater before
it reaches the downslope site.

Using the given data create a standard curve in Excel, and use
Trendline to add a linear regression with the equation. Then use
the standard curve and the dilutions to determine the concentration
of NO_{3}^{-} in all the samples. Using the data
analysis tool pack, perform the appropriate t-test to deduce if the
nitrate concentration upslope is less than or greater than the
nitrate concentration downslope. When performing a t-test using the
data analysis tool pack, the output will include the means for both
groups.

What is the average NO_{3}^{-} concentration at
the upslope site?

- Report your answer, from the data analysis tool pak output, to 3 decimal places

What is the average NO_{3}^{-} concentration at
the downslope site?

- Report your answer, from the data analysis tool pak output, to 3 decimal places

Given the EPA drinking water quality standard is 10 mg/L of
nitrate, is the upslope site safe to drink based only on nitrate
content? (Enter **yes** or
**no**)

Is the downslope site safe to drink, based only on
NO_{3}^{-} concentration? (Enter
**yes** or **no**)

Assuming the two sites are hydrologically well connected, the transit time between the two sites is fast, and the two sites cannot be treated as independent samples, what kind of t-test should be performed to show that the upslope site is greater than the downslope site? Enter the letter of your answer choice in the answer blank

A. one-tailed unpaired t-test

B. two-tailed unpaired t-test

C. one-tailed paired t-test

D. two-tailed paired t-test

What is the calculated t statistic, rounded to 4 decimal places?

Is the calculated t statistic **greater** or
**less** than the critical t value reported by the
data analysis tool pack? (enter **greater**
or **less**)

Is the nitrate concentration at the upslope site significantly
greater than the downslope site? (Enter
**yes** or **no**)

Based on this statistical result, and assuming no diffusion or
dilution occurs between the upslope and downslope site, do you
think microbes are removing NO_{3}^{-} from the
ground water? (Enter **yes** or
**no**)

https://docs.google.com/spreadsheets/d/1yV329xk6EV1aDU0e2WxhFy8_VYCl1m8BK16zW_pqqSA/edit#gid=0

Answer #1

Beer’s Law Data for Salicylic Acid solutions and construction of
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10.0 mL of the stock
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Comparing two means: When drink drove a student to
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(Rubric included)
Instructions
For this assignment, you review this week’s Learning Resources
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correctly saved the data file in Week 2, you may open and use that
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Comparing two means: When drink drove a student to
statistics
(Rubric included)
Instructions
For this assignment, you review this week’s Learning Resources
and then perform a two-sample independent t test and an ANOVA
related to the dataset that was utilized in the week 2 SPSS
application assignment. Import the data into SPSS; or, if you
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