Microsoft Office Tutorials and References

In Depth Information

Research hypothesis H
1
: l
6¼
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

about the mean is:

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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