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 +2.35.
And the absolute value of minus 2.35 (i.e. -2.35) is also +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.
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:
t ¼ X l
S X
ð 4 : 1 Þ
where
s : e : ¼ S X ¼ S
p
n
ð 4 : 2 Þ
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
l from it (remember that the population mean for a study involving numerical
rating scales is the ‘‘middle’’ number in the scale).