> 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/best-medium/identify-best-medium.md).

# Identify best medium

Highest cells/mL means best growth medium. We use a spreadsheet tool for the calculations. Below we will detail how to export the data and perform calculations.

A template is available for download with our data example.

{% file src="/files/rGZyf9q1di28xlhwmlJG" %}

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

## Step by step data analysis

{% stepper %}
{% step %}

#### Export CSV file

Use EXPORT CSV to download a file of comma-separated values.

Open the CSV file in a spreadsheet tool like Excel. Save the file as .xlsx.
{% endstep %}

{% step %}

#### Calculate arithmetic mean

Use a spreadsheet to calculate the arithmetic mean of the three time points for a given growth medium. In excel the formula would be <kbd>=AVERAGE(number1:number3)</kbd>.
{% endstep %}

{% step %}

#### Calculate standard deviation

Use a spreadsheet to calculate the standard deviation of the three time points for a given growth medium. In excel the formula would be <kbd>=STDEV.S(number1:number3)</kbd>.
{% endstep %}

{% step %}

#### Calculate CV

Use a spreadsheet to calculate CV <kbd>= standard deviation / average</kbd>. Change formatting to percent style.
{% endstep %}

{% step %}

#### Plot data for individual replicates

Make a bar chart of the individual replicates. This is exemplified in the left plot below.
{% endstep %}

{% step %}

#### Plot mean and standard deviation

Make a dot plot of the mean and standard deviation. This is exemplified in the right plot below.
{% endstep %}
{% endstepper %}

## Data analysis

Identify the growth medium that has the highest mean cell concentration. In the below example Terrific broth reaches the highest cell concentration. CD is a strong contender for the second place. Contrarily, LB and TSB both result in relatively low cell concentrations. The error bars for LB and TSB are overlapping and therefore it is not possible to determine which if LB leads to higher cell concentrations than TSB.

<figure><img src="/files/JqHhWWJoiemGESGmuBaK" alt=""><figcaption><p><em>E. coli</em> cultivated in four different growth media namely terrific broth (Terrific), Luria-Bertani medium (LB), tryptic soy broth (TSB), and Bacto<sup>TM</sup> CD supreme fermentation production medium (CD). Culture samples were measured on BactoBox® in single replicates after 22, 28 and 35 hours of incubation time. The left plot represents individual measurements while the right plot represents arithmetic means. Standard deviation is represented by error bars. To facilitate the inspection of overlapping error bars, they are vertically elongated with transparent boxes matching the color of each growth medium.</p></figcaption></figure>

## Summary

By now you have ranked your growth media candidates for their ability to support the highest cell concentrations. Next step is [Inspect data critically](/mpd/workflows/best-medium/inspect-data-critically.md) where we explain what caveats you should pay special attention to.


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