> For the complete documentation index, see [llms.txt](https://help.sbtinstruments.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.sbtinstruments.com/mpd/workflows/mpd1/optional-rigorous-approach.md).

# Optional: rigorous approach

In [Inspect data for harvest time](/mpd/workflows/mpd1/inspect-data-for-harvest-time.md) we used a simplistic approach to find the harvest time. Since you have replicates it is possible to use a more rigorous statistical approach.

## Student's *t*-test

The Student's *t*-test is a great way to check if the cell concentrations differ significantly for the data points close to [max cell titer](#user-content-fn-1)[^1]. A seemingly higher arithmetic mean may simply be due to inherent variability. The goal of the *t*-test is to identify the first data point from where cell concentration is no longer increasing significantly.

You can use the Excel template below to perform a *t*-test on your data. Although this step is optional and will likely lead to the same conclusions as the step-by-step guide above, it offers a more rigorous statistical basis for your analysis and can increase confidence in your decisions. The Student's *t*-test is the rigorous approach to the above (simplistic) visual inspection of overlapping error bars.

To do this, you will need to export the data by using the <kbd>EXPORT CSV</kbd> button in the measurement group panel.

<figure><img src="/files/fgue0onNLWJkwdFwynWS" alt="" width="563"><figcaption><p>Example of data export from Access to CSV file. The CSV file is opened in a spreadsheet tool such as Excel.</p></figcaption></figure>

{% file src="/files/lTDRoooJyoUt68KqKcu7" %}

## Harvest algorithm

Admittedly, it is tedious to export data from Access and analyze it in Excel. That is why we are working on curve-fitting features directly in Access. All the tricky math will happen automatically and you get a user-friendly and rigorous approach to choose the best harvest time.

<i class="fa-radio-tuner">:radio-tuner:</i> Stay tuned for updates!

{% hint style="info" icon="hammer-brush" %}

## We are working on a harvest algorithm

The most rigorous approach to determine harvest time is to fit the data to a mathematical function. In the present workflow we use a more simplistic, rule-of-thumb approach.

<i class="fa-radio-tuner">:radio-tuner:</i> Stay tuned. We are working on a when-to-harvest algorithm directly in Access. It will do all the tricky curve-fitting automatically.
{% endhint %}

[^1]: The highest concentration of viable cells achieved in a cell culture during a cultivation process.


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