Microsoft Office Tutorials and References

In Depth Information

4.3 Can You Use Either the 95 Percent Conﬁdence

Interval About the Mean OR the One-Group t-test

When Testing Hypotheses?

You are probably asking yourself:

“It sounds like you could use
either
the 95% conﬁdence interval about the mean
or
the

onegroup t-test to analyze the results of the types of problems described so far in this topic? Is

this a correct statement?”

The answer is a resounding:
“Yes!”

Both the conﬁdence interval about the mean and the one-group t-test are used often in

science research on the types of problems described so far in this topic.
Both of these tests

produce the same result and the same conclusion from the data set!

Both of these tests are explained in this topic because some researchers prefer the

conﬁdence interval about the mean test, others prefer the one-group t-test, and still

others prefer to use both tests on the same data to make their results and conclusions

clearer to the reader of their research reports. Since we do not know which of these

tests your researcher prefers, we have explained both of them so that you are

competent in the use of both tests in the analysis of statistical data.

Now, let’s try your Excel skills on the one-group t-test on these three problems at

the end of this chapter.

4.4 End-of-Chapter Practice Problems

1. Suppose that you have been asked to decide if the average petal length of a

particular plant species grown in the state of Missouri has changed from what it

was ﬁve years ago when the average length of this plant in selected sites in

Missouri was 3.10 centimeters (cm). You have been asked to test your Excel

skills on the hypothetical data given in Fig.
4.5
.

(a) Write the null hypothesis and the research hypothesis on your spreadsheet

(b) Use Excel to ﬁnd the sample size, mean, standard deviation, and standard

error of the mean to the right of the data set. Use number format (2 decimal

places) for the mean, standard deviation, and standard error of the mean.

(c) Enter the critical t from the t-table in Appendix E onto your spreadsheet, and

label it.

(d) Use Excel to compute the t-value for these data (use 2 decimal places) and

label it on your spreadsheet

(e) Type the result on your spreadsheet, and then type the conclusion in plain

English on your spreadsheet

(f) Save the ﬁle as: PETAL3

2. Suppose that you wanted to study the mass (in grams) of rainbow trout

(
Oncorhynchus mykiss
) in a river in southern Colorado in the U.S. Five years

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