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Comparing mortality/survival rate among treatments
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
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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!
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Re: Comparing mortality/survival rate among treatments
@Mark_Bailey 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
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.