# Measurement group

When we group measurements together, we reveal trends in the data. If a single measurement is like a still frame, a group of measurements is the complete film.

Just like the [Measurements](/encyclopedia/software/access/pages/measurements.md) page, we present measurement groups as a spreadsheet.

<div data-with-frame="true"><figure><img src="/files/wU04QBB3MQnzi2FaRKqX" alt=""><figcaption><p>Navigate to the <em>Measurement group</em> page. Open individual measurement groups for analytics, plotting, and reporting.</p></figcaption></figure></div>

## Create measurement group

Press the *Create measurement group...* button to open the dialog (see image below). Fill in the fields and press the *Create* button.

<div data-with-frame="true"><figure><img src="/files/CAIbBuSQa7kY9SMGwlNb" alt=""><figcaption><p>The dialog used to create a new measurement group.</p></figcaption></figure></div>

The *Measurement group name* can be anything. E.g., the name of your experiment or the name of your current batch.

There are three *Measurement group types*:

| Group type                                                                                                  | Analytics                                       | Plotting                       | Reporting  |
| ----------------------------------------------------------------------------------------------------------- | ----------------------------------------------- | ------------------------------ | ---------- |
| [Basic group type](/encyclopedia/software/access/pages/measurement-group/basic-group-type.md)               | No                                              | No                             | PDF report |
| [Correlation group type](/encyclopedia/software/access/pages/measurement-group/correlation-group-type.md)   | Linear regression for CFU-vs-BactoBox® data set | Growth curve, CFU-vs-BactoBox® | PDF report |
| [Growth curve group type](/encyclopedia/software/access/pages/measurement-group/growth-curve-group-type.md) | No                                              | Growth curve, CIZE             | PDF report |

Both *Company name* and *Author* are optional.

## Open measurement group

Click the *Open* button in the leftmost column. This changes the view to a spreadsheet of all executions in the measurement group.

This looks similar to the [Measurements](/encyclopedia/software/access/pages/measurements.md) page, but with columns specific to the group type.

When a group is *open*, the <kbd>Measure</kbd> button opens with the group already selected. This makes it easy to start the *Measure* program and add it to the group as a single action. See the quick clip below for an example.

<div data-with-frame="true"><figure><img src="/files/ugv1jf3viZYunUTNnKsH" alt=""><figcaption><p>Create a measurement group, open it, and press <kbd><mark style="background-color:purple;">Measure</mark></kbd> to start the <em>Measure</em> program. Since the measurement group is <em>open</em>, the newly-started measurement becomes part of the measurement group.</p></figcaption></figure></div>

## Input columns

When you open a measurement group, the following columns are editable:

| Column       | Meaning                                  | Typical use                                                                                        |
| ------------ | ---------------------------------------- | -------------------------------------------------------------------------------------------------- |
| *Label*      | Grouping key for plots and reports.      | Species name, bioreactor name, experiment name, etc.                                               |
| *Dilution*   | Dilution factor used for the sample.     | `1000` for a 1:1000 dilution.                                                                      |
| *Sampled at* | Timestamp for when the sample was taken. | Bioreactor, shake flask, etc.                                                                      |
| *HPI*        | Hours post-inoculation.                  | Manual time axis input.                                                                            |
| *calcHPI*    | Calculated hours post-inoculation.       | Auto time axis when *HPI* is missing. See [how calcHPI is calculated](#how-calchpi-is-calculated). |
| *Notes*      | Free-text metadata.                      | Comments, deviations, etc.                                                                         |

#### How *calcHPI* is calculated

1. If *HPI* is available, *calcHPI* = *HPI*.
2. If *HPI* is missing, but *Sampled at* is available, we calculate *calcHPI* from the first measurement for the same *Label*.
3. If both *HPI* and *Sampled at* are missing, *calcHPI* is empty.

Remember to press *Save* to persist your changes.


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