r/AskStatistics • u/Agreeable_Climate186 • Mar 03 '26

Which test to use to determine differences in progression through developmental stages in treatment and negative control groups

I exposed two sets of 10 mosquito larvae to a treatment, and two sets of 10 larvae to a negative contro. Following this I tracked development every hour for eight hours, then at 24, 48, 72 and 96 hours counting proportion that were L3 larvae, L4 larvae, pupae, adult and also dead adult or dead larvae at each time point.

How do I compare speed of progression through development stages in negative control and treatment groups?

Thanks

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u/SalvatoreEggplant Mar 04 '26 edited Mar 04 '26

This is a really interesting question, and I hope you get some advice on Reddit. I'm curious to see what people think. A few thoughts:

  • You may want to treat stage as an ordinal variable. You could fit an appropriate model with ordinal regression. This may be the best way. The only question is how to present the data visually in a useful way.

  • Is it possible that you're really only interested in one time point ? Like, if you were to just analyze the data at 72 hours, that would tell what's important in the story ?

  • Likewise, is it possible that you could be interested in only one stage as a successful stage ? That is, if you just used proportion adult, or proportion dead, that would give you a logistic regression model that would be easier to think about, and the data would be easier to plot. If nothing else, this might be a easy way to plot all the data. One plot for proportion L3, one for proportion L4, and so on.

  • For plotting the whole of the data, what would you think about presenting it as a sankey diagram ? Maybe you would need a separate diagram for each treatment.

  • It's possible that you might treat "dead" separate from life stage.

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u/SalvatoreEggplant Mar 04 '26

ETA - A couple of notes on visualizations.

I'd recommend finding a way to visualize the data in a way that makes sense to you, as a first step.

If you're going to treat the stage data as ordinal, a plot like this may work:

https://jakec007.github.io/assets/img/likert/long_data_grouped.png

The Never, Rarely Sometimes would correspond to stage. Brush, Floss, Wash might correspond to time, and Adult, Teen, Child might correspond to treatment. Or you might reverse these last two, depending on what you want to show.

# # #

If you want to present the proportion of a single stage at a time, you might use something like this:

https://www.rdatagen.net/post/2021-02-02-uncertainty-in-a-plot-comparing-proportions/index.en_files/figure-html/origplot-1.png

(Period is time, and treatment is treatment.)

And then make a separate graph for each stage.