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Comparing mortality/survival rate among treatments

Sep 10, 2020 11:49 AM
(170 views)

What is the best method to analyze percent mortality or percent survival (100-mortality) data? I am providing a mock data set. I place 20 animals in a cage and at the end of the study I count the number of live animals and the difference from 20 is the dead animals. The experimental design is a complete randomize block design and I want to use block as either a random effect, covariable, or other suggestion. Time of death is no important and thus I'm struggling to use the JMP survival tools. I want to know if there is a statistical difference in mortality or survival rate (as a percent) among the 3 treatments. If I calculate by hand survival_% is: Control=97%, Drug=88%, Placebo=79.5%; and thus mortality_% is: Control=3%, Drug=12%, Placebo=20.5%.

Please provide step-by-step instructions (e.g., Analyze > Fit Model > etc.) or pictures.

Thanks,

Cage Block Treatment Initial_count Final_count Survival_% Deaths Mortality_%

1 1 Drug 20 20 100 0 0

2 1 Control 20 19 95 1 5

3 1 Placebo 20 16 80 4 20

4 2 Placebo 20 17 85 3 15

5 2 Drug 20 16 80 4 20

6 2 Control 20 20 100 0 0

7 3 Control 20 19 95 1 5

8 3 Placebo 20 15 75 5 25

9 3 Drug 20 18 90 2 10

10 4 Placebo 20 14 70 6 30

11 4 Control 20 20 100 0 0

12 4 Drug 20 19 95 1 5

13 5 Placebo 20 15 75 5 25

14 5 Control 20 20 100 0 0

15 5 Drug 20 17 85 3 15

16 6 Drug 20 18 90 2 10

17 6 Placebo 20 17 85 3 15

18 6 Control 20 20 100 0 0

19 7 Placebo 20 16 80 4 20

20 7 Drug 20 18 90 2 10

21 7 Control 20 20 100 0 0

22 8 Drug 20 17 85 3 15

23 8 Placebo 20 16 80 4 20

24 8 Control 20 19 95 1 5

25 9 Control 20 18 90 2 10

26 9 Drug 20 17 85 3 15

27 9 Placebo 20 16 80 4 20

28 10 Placebo 20 17 85 3 15

29 10 Drug 20 16 80 4 20

30 10 Control 20 19 95 1 5

3 REPLIES 3

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Re: Comparing mortality/survival rate among treatments

This case is a classic application of 'probit analysis.'

- Select Analyze > Fit Model.
- Select Initial Count and Final Count (in that order), then click Y.
- Select the other data columns that you want to use as factors and click Add.
- Click Personality and select Generalized Linear Model.
- Click Distribution and select Binomial.
- Click Link and select Probit.
- Click Run.

That should do it.

I have to say that this process is backward: collect the data and then decide on the analysis. The choice of the analysis should dictate the data collection.

Hope that these instructions help!

Learn it once, use it forever!

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@markbailey thank you for the suggestion. Unfortunately it does not work, I have tried the binomial distribution with not successful results; it does not accept a random variable or covariable. Please try to use the mock data set I provided to see if you can find a suggestion. Cheers,

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Re: Comparing mortality/survival rate among treatments

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Re: Comparing mortality/survival rate among treatments

You are correct. The GLM platform does not accept terms for random effects. The JMP Pro Mixed Model platform does not accept non-normal error distributions.

Learn it once, use it forever!