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Local government is worried that runoff from a corporate farm has caused water in a nearby stream to become acidic. The pH is used to measure the acidity/alkalinity of a substance. Pure water, for instance, has a pH of 7, and smaller pH values indicate acidity, while larger values indicate alkalinity. A contractor is hired to test the hypothesis that the water is significantly acidic. pH values appear to be normally distributed.

This problem uses StatCrunch.

A local greenhouse sells coffee-tree saplings. They price their saplings based on the height of the plant. They have two workers, Susan and Karen, who measure the saplings for pricing. The greenhouse manager wants to determine if there is a significant difference in the measurements made by these two individuals. She has them measure the same set of 15 saplings. Assume that the differences are calculated as Susan - Karen.

A local greenhouse sells coffee-tree saplings. They price their saplings based on the height of the plant. They have two workers, Susan and Karen, who measure the saplings for pricing. The greenhouse manager wants to determine if there is a significant difference in the measurements made by these two individuals. She has them measure the same set of 15 saplings. Assume that the differences are calculated as Susan - Karen.

First, log in to StatCrunch by clicking the link. You do not need to do anything else to log in. If a blank spreadsheet appears, you've logged in.

The resulting measurements (in cm) have been saved in StatCrunch(opens in new window). Use the data to compute the test statistic for the difference between Susan and Karen. For help using StatCrunch for a Paired Difference T-Test click here(opens in new window). (You may want to right-click that link and open it in a new window so you don't lose your answers on this quiz!)

Give your answer to four decimal places.

The resulting measurements (in cm) have been saved in StatCrunch(opens in new window). Use the data to compute the test statistic for the difference between Susan and Karen. For help using StatCrunch for a Paired Difference T-Test click here(opens in new window). (You may want to right-click that link and open it in a new window so you don't lose your answers on this quiz!)

Give your answer to four decimal places.

From this hypothesis test, choose the correct conclusions.

Select one or more:

We reject the null hypothesis.

We fail to reject the null hypothesis.

We conclude that there is a significant statistical difference between the two employees' measurements.

We conclude that there is not a significant statistical difference between the two employees' measurements.

On average in the sample, Susan has larger values than Karen.

On average in the sample, Karen has larger values than Susan.

We can not tell whether Susan or Karen has larger values on average.

Select one or more:

We reject the null hypothesis.

We fail to reject the null hypothesis.

We conclude that there is a significant statistical difference between the two employees' measurements.

We conclude that there is not a significant statistical difference between the two employees' measurements.

On average in the sample, Susan has larger values than Karen.

On average in the sample, Karen has larger values than Susan.

We can not tell whether Susan or Karen has larger values on average.

A dessert manufacturer wanted to know if adding a preservative to their cupcakes extended their shelf life before going stale. They found the cupcakes that had the preservative lasted seven days before going stale, but the cupcakes without the preservative only lasted three days. They found that the difference in these shelf lives had a p-value of 0.24. Assume an α of 0.05.

What should we conclude about their findings?

Select one:

The results were statistically significant and practically significant.

The results were statistically significant but not practically significant.

The results were not statistically significant but were practically significant.

The results were neither statistically significant nor practically significant.

What should we conclude about their findings?

Select one:

The results were statistically significant and practically significant.

The results were statistically significant but not practically significant.

The results were not statistically significant but were practically significant.

The results were neither statistically significant nor practically significant.