8.2.3.2.1 - Minitab Express: 1 Sample Mean t Test, Raw Data

8.2.3.2.1 - Minitab Express: 1 Sample Mean t Test, Raw Data

MinitabExpress – One Sample Mean t Test Using Raw Data

Research question: Is the mean GPA in the population different from 3.0?

Null hypothesis: $\mu$ = 3.0
Alternative hypothesis: $\mu$ ≠ 3.0

The GPAs of 226 students are available.

A one sample mean $t$ test should be performed because the shape of the population is unknown, however the sample size is large ($n$ ≥ 30).

To perform a one sample mean $t$ test in Minitab Express using raw data:

1. Open Minitab data set:
2. On a PC: Select STATISTICS > One Sample > t
On a Mac: Select Statistics > 1-Sample Inference > t
3. Double-click on the variable GPA to insert it into the Sample box
4. Check the box Perform a hypothesis test
5. For the Hypothesized mean enter 3
6. Click the Options tab
7.  Use the default Alternative hypothesis of Mean ≠ hypothesized value
8. Use the default Confidence level of 95
9. Click OK

This should result in the following output:

1-Sample t: GPA
N Mean StDev SE Mean 95% CI for $\mu$
226 3.23106 0.51040 0.03395 (3.16416, 3.29796)

$\mu$: mean of GPA

Null hypothesis H0: $\mu$ = 3 H1: $\mu$ ≠ 3
T-Value P-Value
6.81 <0.0001
Video Walkthrough

Select your operating system below to see a step-by-step guide for this example.

We could summarize these results using the five step hypothesis testing procedure:

1. Check assumptions and write hypotheses

We do not know if the population is normally distributed, however the sample size is large ($n \ge 30$) so we can perform a one sample mean t test.

$H_0: \mu = 3.0$
$H_a: \mu \ne 3.0$

2. Calculate the test statistic

$t (225) = 6.81$

3. Determine the p-value

$p < 0.0001$

4. Make a decision

$p \le \alpha$, reject the null hypothesis

5. State a "real world" conclusion

There is evidence that the mean GPA in the population is different from 3.0

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