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5.1.3 STEP 3: State the Null Hypothesis and the Research

Hypothesis for the Two-Group t-Test

If you have completed Step 1 above, this step is very easy because the null

hypothesis and the research hypothesis will always be stated in the same way for

the two-group t-test. The null hypothesis states that the population means of the

two groups are equal, while the research hypothesis states that the population

means of the two groups are not equal. In notation format, this becomes:

H
o
: l
1
¼
l
2

H
1
: l
1

6¼
l
2

You can now see that this notation is much simpler than having to write out the

names of the two groups in all of your formulas.

5.1.4 STEP 4: Select the Appropriate Statistical Test

Since this chapter deals with the situation in which you have two groups but only

one measurement on each person, plant, or animal in each group, we will use the

two-group t-test throughout this chapter.

5.1.5 STEP 5: Decide on a Decision Rule for the Two-Group t-Test

The decision rule is exactly what it was in the previous chapter (see
Sect. 4.1.3
)

when we dealt with the one-group t-test.

(a) If the absolute value of t is less than the critical value of t, accept the null

hypothesis.

(b) If the absolute value of t is greater than the critical value of t, reject the null

hypothesis and accept the research hypothesis.

Since you learned how to ﬁnd the absolute value of t in the previous chapter

(see
Sect. 4.1.3.1
)
, you can use that knowledge in this chapter.

5.1.6 STEP 6: Calculate the Formula for the Two-Group t-Test

Since we are using two different formulas in this chapter for the two-group t-test

depending on the sample size in the two groups, we will explain how to use those

formulas later in this chapter.

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