Knowledge Base

Group Statistics and Charts

With Group Statistics, you can calculate the statistics of parameters, grouped per treatment group × time point combination, and view the corresponding charts.

Procedure

1. Make sure you have selected the right Data Segmentation profile and Parameter profile. Data not selected in these profiles are not included in the results.
2. Choose Analyze > View Group Statistics and Charts.
3. Under Numerical Results, click a category tab to display the results.
4. Under Graphical Results, click a category to view the corresponding parameter charts.
5. To export group statistics and charts, see the Export section.

Notes

• If the tab for a parameter contains no results, it means that it is not selected in the currently active Parameter profile. To select another Parameter profile, in the Profiles Explorer, right-click a Parameter profile and select Set as Active.
• If your experiment contains one or more runs with missing or corrupt data, you get an error message when you try to open the group statistics and charts. In the Experiment Explorer, delete the runs listed in the error message by right-clicking a run and selecting Delete.

Statistics Available

To calculate group statistics, CatWalk XT uses the values of trial statistics. For example, the experimental group Control includes 10 trials for 10 subjects recorded at time point Day 1. The group mean of Print Length for Control - Day 1 is calculated by averaging the 10 per-trial values of Print Length for that group. You can find the per-trial values in the Trial Statistics export file.

The following statistics are available:

• N – The number of trials in that treatment group × time point combination.
• Mean (for all parameters except Phase Dispersions and Couplings) – The arithmetic mean of the parameter for that treatment group × time point combination.
• CStat Mean (only for Phase Dispersions and Couplings) – The circular mean of phase lags (CStat) for that treatment group × time point combination. Note that values like -49% and +51% may look different in a column chart, but in the circular domain they are very similar.
• CStat R (only for Phase Dispersions and Couplings) – The length of the vector representing the average phase lag for a treatment group × time point combination.
• SEM (for all parameters except Phase Dispersions and Couplings) – The Standard Error of the Mean of the parameter.
• CStat AD (only for Phase Dispersions and Couplings) – The angular deviation of the individual phase lags for a treatment group × time point combination.
• CStat SD (only for Phase Dispersions and Couplings) – The circular standard deviation of the individual phase lags for a treatment group × time point combination.

Chart Settings

In the Group Statistics & Charts screen, under Graphical Results, open the Chart Settings window. The following settings are available:

Chart Type

• Bar Chart – Shows the mean value of the parameter as a colored bar and the standard error as an error bar.
• Five Number Summary Chart – A box-whisker chart showing the sample minimum, lower quartile, median, upper quartile, and sample maximum. This chart can be made when at least 4 trials (N ≥ 4) are available for that data series. This chart type is not displayed for Phase Dispersions and Couplings.

Horizontal Axis

• Time Points – Displays the time points on the horizontal axis.
• Treatment Groups – Displays the treatment groups on the horizontal axis.

Data Series

Data Series are displayed in the chart legend. You have the same options as under Horizontal Axis. If you change the option under Horizontal Axis, the option under Data Series changes automatically and vice versa.

Title Font Size

Select the size in pixels of the font for the chart title (range: 6–14).

Bar Chart / Five Number Summary Chart

• Chart Width – The width of the chart in pixels (including the legend).
• Chart Height – The height of the chart in pixels (including the title).

Bar Chart Settings

• Bar width (%) — The percentage of the space available for that data series occupied by the bar.
• Gap — The gap between bars (in pixels).
• Whisker width (%) — The width of the whisker relative to the bar width.

Circular Charts

• Chart size — The width and the height of the chart in pixels, including the title and the legend. Range: 100–1000.
• Include datapoints — Select this option if you want to have the per-trial values of variables displayed on the circle. Those data points are used to calculate the group average, which is represented by the vector. Note: Data points may overlap on the circle. In that case you see fewer dots than the actual number of trials in that group. However, the statistics are based on all trials in each group.
• Split charts by — Select which criterion you want to produce different charts:
  • Treatment Groups. For example, two treatment groups results in two charts per variable, one for Control and one for Treated. The time points appear in the legend.
  • Time Points. For example, three time points (d1, d5, d10) results in three charts per variable. The treatment groups appear in the legend.
  • Time Points and Treatment Groups. This option creates as many charts as those created with the two options above, taken together. For example, with three time points and two treatment groups, for the variable Phase Dispersions RF->LH: the first three charts are based on the three time points and the legend shows the groups of subjects. The other two charts show the same data the other way round: one chart for each group of subjects, with the legend showing the three time points.

If a chart is empty, it could be that a five number summary chart is selected, and for that parameter less than four trials are available. To solve this, in the Chart Settings window select Bar chart next to Chart type.

To optimize the space needed for charts, reduce the font size for the title, and in the Experiment settings shorten the name of the categories under Treatment Groups and Time Points. That makes the legend smaller.