Bioequivalence and Bioavailability Forum • Groups: Overlapping CIs

Groups: Overlapping CIs [Design Issues]

posted by Helmut – Vienna, Austria, 2024-11-05 11:12 (26 d 06:35 ago) – Posting: # 24260
Views: 1,016

Hi BEQool,

❝ Like you said in the other post ("Even if an assessor would calculate the confidence interval of groups separately, likely they would overlap due to the limited sample sizes."), they most likely overlap because of the relatively small sample size (n=12 per group). Probably if we had larger total sample size (in this example it would maybe be reasonable as CVw is around 27%, e.g. total sample size of 32 or 36 subjects) and thus larger sample size per group then groups' 90% CI most likely wouldnt overlap.

❝ I am just wondering if variabilty is moderate and the sample size is large enough (--> high power) then in most cases groups' 90% CI probably wouldnt overlap in case of significant G*T interaction?

You are right:

Simulated data n = 36 group 1: n = 18, mue = 0.80 group 2: n = 18, mue = 1.25 Model I (pooled data) p(G×T) = 0.014978 Model II (pooled data) PE = 112.86% 90% CI = 101.14 – 125.93% CVw = 28.01% Model III (group 1) PE = 96.75% 90% CI = 81.55 – 114.79% CVw = 30.02% Model III (group 2) PE = 131.64% 90% CI = 116.71 – 148.49% CVw = 20.91%

However, how realistic is \(\small{\mu_1=0.80,\,\mu_2=1/\mu_1}\)?

Let’s try a less extreme case with \(\small{\mu_1=0.825,\,\mu_2=1/\mu_1}\):

Simulated data n = 32 group 1: n = 16, mue = 0.825 group 2: n = 16, mue = 1.2121 Model I (pooled data) p(G×T) = 0.040949 Model II (pooled data) PE = 103.96% 90% CI = 92.58 – 116.73% CVw = 27.80% Model III (group 1) PE = 90.57% 90% CI = 75.27 – 108.96% CVw = 30.37% Model III (group 2) PE = 119.33% 90% CI = 104.67 – 136.03% CVw = 21.28%

\(\small{p(\text{G}\times\text{T})}\) is significant and CIs of groups overlap. :-D

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Complete thread:

Possible reasons for group effect GM 2019-07-20 07:36 [Design Issues]
- Group “effect” Helmut 2019-07-20 14:02
- Possible reasons for group effect ElMaestro 2019-07-20 19:20
  - Possible reasons for group effect GM 2019-07-23 06:23
    - “Group-by-Treatment Interaction” Helmut 2019-07-23 10:32
      - “Group-by-Treatment Interaction” BEQool 2024-10-22 12:39
        
        “Group-by-Treatment Interaction” Helmut 2024-10-22 12:47
        
        OT: A choice between mittyri 2024-10-22 16:03
        
        OT: A choice between BEQool 2024-10-23 11:02
        
        OT: A choice between Helmut 2024-10-23 11:58
        
        OT: A choice between BEQool 2024-10-23 13:17
        
        OT: A choice between Helmut 2024-10-23 13:22
        Groups: Overlapping CIs Helmut 2024-11-03 11:36
        
        Groups: Overlapping CIs BEQool 2024-11-05 09:14
        
        Groups: Overlapping CIsHelmut 2024-11-05 10:12
        
        Groups: Overlapping CIs BEQool 2024-11-06 07:44
        
        Groups: (Hardly‽) overlapping CIs Helmut 2024-11-21 13:20
        
        Groups: (Hardly‽) overlapping CIs BEQool 2024-11-22 12:32
        
        Groups: (Hardly‽) overlapping CIs Helmut 2024-11-22 12:58
        Multiplicity? Helmut 2024-11-23 13:05
        
        Groups BEQool 2024-11-26 08:15