Microsoft Office Tutorials and References
In Depth Information
Research hypothesis H 1 : l 4
STEP 2: Select the appropriate statistical test
In this chapter we are studying the conﬁdence interval about the mean, and so
we will select that test.
STEP 3: Calculate the formula for the statistical test
You will recall (see Sect. 3.1.5 ) that the formula for the conﬁdence interval
X ts : e :
ð 3 : 2 Þ
We discussed the procedure for computing this formula for the conﬁdence
interval about the mean using Excel earlier in this chapter, and the steps involved
in using that formula are:
1. Use Excel’s = count function to ﬁnd the sample size.
2. Use Excel’s = average function to ﬁnd the sample mean, X .
3. Use Excel’s = STDEV function to ﬁnd the standard deviation, STDEV.
4. Find the standard error of the mean (s.e.) by dividing the standard deviation
(STDEV) by the square root of the sample size, n.
5. Use Excel’s TINV function to ﬁnd the lower limit of the conﬁdence interval.
6. Use Excel’s TINV function to ﬁnd the upper limit of the conﬁdence interval.
STEP 4: Draw a picture of the conﬁdence interval about the mean, including the
mean, the lower limit of the interval, the upper limit of the interval, and the
reference value given in the null hypothesis, H 0 (We will explain Step 4 later in the
chapter).
STEP 5: Decide on a decision rule
(a) If the reference value is inside the conﬁdence interval, accept the null
hypothesis, H 0
(b) If the reference value is outside the conﬁdence interval, reject the null
hypothesis, H 0 , and accept the research hypothesis, H 1
3.2.3.6
STEP 6: State the result of your statistical test
There are two possible results when you use the conﬁdence interval about the
mean, and only one of them can be accepted as ‘‘true.’’ So your result would be
one of the following:
Either: Since the reference value is inside the conﬁdence interval,
we accept the null hypothesis, H 0
Or: Since the reference value is outside the conﬁdence interval,
we reject the null hypothesis, H 0 , and accept the research
hypothesis, H 1
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