# Faq how do I calculate my own T2 and Q limits

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### Issue:

How do I calculate my own T2 and Q limits?

### Possible Solutions:

Confidence limits for Q residuals (also known as "SPE") and Hotellings T2 can be calculated using the commands:

```>> residuallimi
>> tsqlim
```

To calculate new residual limits, you must pass the eigenvalues for the residuals from the model. Assuming you have a model structure named "model":

```>> qlimit = residuallimit(model.detail.reseig,cl);
```

where `cl` is the confidence limit desired (in fractional confidence limit: 0.95 ). Note that for some model types, `.detail.reseig` is not defined. In these cases, you'll need to calculate the raw residuals themselves. You can usually do this with `datahat`, but you need to pass the original calibration data along with the model:

```>> [xhat,residuals] = datahat(model,data);
>> qlimit = residuallimit(residuals,cl);
```

To calculate new T2 limits, `tsqlim` can be called very simply:

```>> tsqcl = tsqlim(m,pc,cl);
```

where `m` is the number of samples in the model, `pc` is the number of PCs (or LVs) in the model, and `cl` is the confidence limit desired.

Note that `tsqlim` supplies the same result whether `cl` is a percent or fractional but `residuallimit` requires the fraction `cl`.

To calculate limits for individual scores, see the related FAQ.

Still having problems? Please contact our helpdesk at helpdesk@eigenvector.com