# Column n Is Too Small

Where the Column n shown in Statistics - Below is smaller than expected, this is usually due to missing data.

## How Column n is computed

Column n shown in Statistics - Below is computed using the default NET on a table. For example, on the table shown below to the right, you can see that the Column n shown at the base of the table is the same as that shown in the NET row.

## How to investigate the problem

The existence of the problem is most readily seen by looking at the base n information shown on the bottom-right corner of Q. If it shows a range, such as in the two examples below (base n = from 314 to 327), this signifies that there is missing data on the table and that the Column n will, as a result, be relatively small.

By selecting Statistics - Cells > Column n, you can see that the NET row's Column n aligns with that from Statistics - Cells. In the example above to the right you can see that although the Column n is 160 in most cells in the first column, it drops to 156 for Pepsi Light, NET and the Column n row.

The most informative way of examining the problem is usually to create a SUMMARY table (i.e., remove the question shown in the Brown Drop-down Menu), and select n, Base n and Missing n from Statistics - Cells. In the example shown on to the left, we can see the reason the Column n of 314 is less than 327 is due to the 13 respondents with missing data for Pepsi Light (see also NET with missing data).

## "Fixing" the problem

### Fixing the missing data

The most straightforward way to increase the Column n is to:

1. Right-click on one of the row headings and select Values and modify the Value Attributes.
2. Un-checking Missing data.
3. And, if required, Select the cells showing the value of the NET, right-click and create a Filter.

However, often this will an unwanted side-effect, whereby the percentages on the table will change. For example, with the data shown above, Pepsi Light's value of 17% is compute as 52 divided by 314, and if its Base n is changed to 327, the percentage drops to 16%.

### Using Custom Rules

By creating a Custom Rule you can over-ride the formulas used by Q to compute the Column n. However, keep in mind if doing this that Q's approach is based on the principle of conservativism - it minimizes the chance that a user of the research will rely upon an unreliable finding. Any approach which puts a higher Column n than that used by Q runs the risk that users of the research will believe the data to be more robust than is the case. One example of such a rule is Modifying Tables or Plots - Show Maximum Column n In Statistics Below.