Hi,

There are two ways of doing it. One option is using a x-bar control chart, and modify it to plot only one standard deviation from the mean. It can be done in MINITAB, but I'm not really sure how

. The graph is obtained in the

*Stats>>Control Charts*
Now, I'll try to explain the process I know: it may not be the best one but I hope it helps.Well, let's assume you have your data in MINITAB, stored in a single column.

**1.**First you calculate bothe mean and standard deviation. Go to

*Stats>>Display Descriptive Stats* and choose the column of your data.

**2.**Once you have the values for both mean and standard deviations, let's do the graph. You can graph it in the

*Graph>>Time Series Graph* Menu. Choose a single graph and add the column where your data is stored.

**3.**After the graph appears, right click on it and choose from the contextual menu the option

*add*. A submenu will appear where you will see the option

*reference lines*.

**4.**Now in the section titled "Show reference line as Y values" just type the number you got from the mean.

**5.**Repeat both 3 and 4 to add more lines for "mean+1 sd" and "mean-sd"

Any questions, please feel free to ask