NOTE: Now that you have opened Excel, please "File, Save As" and save
this spreadsheet to your hard drive. This will enable all macros to work properly.
After "File, Save As", you will need to exit the browser (Internet Explorer) and
open it in Excel.
If SPC menu item does not
appear when workbook is
opened, click here to load menu.
Help Menu for SPC Workbook
1. Overview
2. Descriptive Statistics
3. Histogram
4. Capability Histogram
5. Control Charts ( X & MR, Xbar & R, Xbar & s)
1. Overview Return to top
This tool was created to assist in the interpretation of data. Various forms are available
for this interpretation (descriptive statistics, histograms, control charts). This worksheet
is ideally suited for moderate sample sizes(<500). Larger sample sizes can be
accomodated but at a cost of higher processing time.
2. Descriptive Statistics Return to top
A descriptive statistics menu item is available to help summarize data. This option is
very flexible in that it allows you to select multiple columns to summarize. Once the
menu item is selcted, make sure the cursor is in the data range box and select the
column(s) you want stats for. Next, select the stats desired by clicking in the
checkboxes. The following statistics are available:
Average The arithmetic mean of a sample of data
Standard Deviation Is a measure of how widely values are dispersed around the mean
or average.
Standard Error Is a measure of the sampling distribution variability for averages
Min The minimum value in a data set
Max The maximum value in a data set
Range The maximum minus the minimum value in a data set. The total spread of th
Skewness A measure of the degree of assymmetry in a data set.
Kurtosis A measure of the degree of peakedness in a data set.
n The number of samples in the data set.
Example:
1 Click on the SPC Menu and select the Descriptive Statistics item.
2. Place the cursor in the Data box and then select the range of data from the worksheet.
In this example, I have selected the data range that includes net contents, brix, and ratio.
Do not select the entire columns, just the general data range of interest. It is okay to
have blank cells.
Click the check boxes to include the summary statistics of interest. N this case I have
chosen all except for skewness and kurtosis.
Also, I the column titles were included in the first row of the selection, check that box.
You may also specify the number of decimal places for the utput.
3. Place the cursor in the Output Cell box. Select a cell in the workbook in which you
want the output to be printed. Be careful not to select a cell that will cause data to be
overwritten.
3. Histogram Return to top
A histogram is an easy tool to help summarize data. The data is grouped into intervals
and plotted like a bar graph. This option also allows you to print a normal curve on top
of the histogram. If the histogram appears normally distributed, we can make prediction
about the areas underneath the curve.
Example:
Once the menu item is selcted, position the cursor inside the data range box and then go
to the worksheet and select the range of data. Enter a title and the number of decimal
places to display. You can also select to print the normal curve on the histogram and
you can enter a default number of classes to include in the histogram. When you are
satisfied with your selections, click okay. A new chart sheet, containing a histogram,
will be added to the workbook.
4. Capability Histogram Return to top
This option prints a histogram and does a capability analysis. In addition to the normal
entries, enter the specification limits and an estimate of process standard deviation,
obtained from a control chart. If you do not have this information, the program will
estimate it from the sample standard deviation. A new chart sheet, containing the
analysis, will be added to your workbook.
5 Control Charts Return to top
There are three menu items for contol charts. Choose the type of chart that fits the data
you have collected. X and MR if individual observations were recorded over time, or
Xbar and R/s if subgrouped data was collected over time. A chart sheet, containing the
control charts, will be added to the workbook.
