Microsoft Office Tutorials and References

In Depth Information

If you took a basic algebra course in high school, you may remember the concept

of “absolute value.” In mathematical terms, the absolute value of any number is

always
that number expressed as a positive number.

For example, the absolute value of 2.35 is

þ

2.35.

─

þ

2.35.

This becomes important when you are using the t-table in Appendix E of this

book. We will discuss this table later when we get to Step 5 of the one-group t-test

where we explain how to ﬁnd the critical value of t using Appendix E.

And the absolute value of minus 2.35 (i.e.

2.35 ) is also

4.1.4 STEP 4: Calculate the formula for the one-group t-test

Objective
: To learn how to use the formula for the one-group t-test

The formula for the one-group t-test is as follows:

X

m

s
X

t

¼

where

(4.1)

s

s

e

:
¼

S
X
¼

p

n

(4.2)

:

This formula makes the following assumptions about the data (Foster, Stine, and

Waterman 1998): (1) The data are independent of each other (i.e., each person

receives only one score), (2) the
population
of the data is normally distributed, and

(3) the data have a constant variance (note that the standard deviation is the square

root of the variance).

To use this formula, you need to follow these steps:

1. Take the sample mean in your research study and subtract the population mean

m

from it (remember that the population mean for a study involving numerical

rating scales is the “middle” number in the scale).

2. Then take your answer from the above step, and divide your answer by the

standard error of the mean for your research study (you will remember that you

learned how to ﬁnd the standard error of the mean in Chapter 1; to ﬁnd the

standard error of the mean, just take the standard deviation of your research

study and divide it by the square root of
n
, where
n
is the number of people,

plants, or animals used in your research study).

3. The number you get after you complete the above step is the value for
t
that

results when you use the formula stated above.

Search JabSto ::

Custom Search