# 4.5 - Bootstrapping in Minitab Express

In this lesson you have learned how to construct bootstrap confidence intervals using StatKey. Minitab Express can also be used to construct bootstrap confidence intervals for a single mean, a single proportion, or the difference between two independent means using the percentile method. Below are two examples.

## MinitabExpress – Bootstrap Confidence Interval for a Proportion

To construct a 95% bootstrap confidence interval for the proportion of students who smoke cigarettes:

1. Open the data set:
2. On a PC: Select Statistics > Resampling > Bootstrapping > 1-Sample Proportion
On a Mac: Select Statistics > Resampling > Bootstrapping for 1-Sample Proportion
3. Double click the variable Smoke Cigarettes in the box on the left to insert the variable into the Sample box
4. Use the largest number of resamples, 1000
5. Click on the Options tab
6. The default is a Two-sided confidence interval at the 95% confidence level
7. Click OK

This should result in output similar to the output below. Note that your results may be slightly different due to random sampling variation.

Observed Sample
Variable N Proportion
Smoke Cigarettes 226 0.07522
Bootstrap Samples for Proportion
Number of Resamples Average 95% CI for Proportion
1000 0.07645 (0.04425, 0.11062)
Video Walkthrough

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

## MinitabExpress – Bootstrap Confidence Interval for a Mean

To construct a 95% bootstrap confidence interval for the mean GPA:

1. Open the data set:
2. On a PC: Select Statistics > Resampling > Bootstrapping > 1-Sample Mean
On a Mac: Select Statistics > Resampling > Bootstrapping for 1-Sample Mean
3. Double click the variable GPA in the box on the left to insert the variable into the Sample box
4. Use the largest number of resamples, 1000
5. Click on the Options tab
6. The default is a Two-sided confidence interval at the 95% confidence level
7. Click OK

This should result in output similar to the output below. Note that your results may be slightly different due to random sampling variation.

Observed Sample
Variable N Mean StDev Variance Sum Minimum Median Maximum
GPA 226 3.23106 0.51040 0.26050 730.220 0.00000 3.30000 4.00000
Bootstrap Samples for Mean
Number of Resamples Mean StDev 95% CI for $$\mu$$
1000 3.23288 0.03330 (3.16261, 3.29863)
Video Walkthrough

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

Note: When using StatKey you were told to take at least 5,000 resamples. Unfortunately, at this time Minitab Express will only take a maximum of 1,000 resamples at a time. For this reason your results may vary more in Minitab Express than in StatKey.