## Sample size estimation for parallel design [Power / Sample Size]

Dear all,

I have data from a parallel pilot study and am using that to estimate the sample size for a pivotal study. The formula that I am using requires an estimate of the inter subject variability which I don't have. I have the total variability (sqrt(MSE)). Is there a way to estimate intersubject variability from a parallel design or would it be correct to use the total variability instead?

Would it be correct to estimate inter-subject var as sd/mean for test and reference separately and then take the average?

And one last question, how correct is it to take 60% of inter subject (calculated as sd/mean) to be the intrasubject variability?

Thanks in Advance!

Nav Coelho

I have data from a parallel pilot study and am using that to estimate the sample size for a pivotal study. The formula that I am using requires an estimate of the inter subject variability which I don't have. I have the total variability (sqrt(MSE)). Is there a way to estimate intersubject variability from a parallel design or would it be correct to use the total variability instead?

Would it be correct to estimate inter-subject var as sd/mean for test and reference separately and then take the average?

And one last question, how correct is it to take 60% of inter subject (calculated as sd/mean) to be the intrasubject variability?

Thanks in Advance!

Nav Coelho

### Complete thread:

- Sample size estimation for parallel designNav Coelho 2007-07-20 16:14 [Power / Sample Size]
- Parallel designs (total variance) Helmut 2007-07-20 16:29
- Parallel designs (total variance) Nav Coelho 2007-07-20 18:38
- CV-intra # 60% CV-inter Helmut 2007-07-22 01:17
- total (pooled) variance: examples Helmut 2007-07-23 17:44
- total (pooled) variance: examples Nav Coelho 2007-07-23 19:58
- total (pooled) variance: examples BEQool 2023-04-18 09:59
- Higher-Order Crossovers Helmut 2023-04-20 10:19
- Higher-Order Crossovers BEQool 2023-04-21 07:53

- total (pooled) variance: examples zizou 2023-04-21 21:23
- total (pooled) variance: examples BEQool 2023-04-22 18:20
- total (pooled) variance: examples zizou 2023-04-22 21:06
- total (pooled) variance: examples BEQool 2023-04-25 10:57
- total (pooled) variance: examples zizou 2023-04-25 22:43
- total (pooled) variance: examples BEQool 2023-05-04 08:17

- total (pooled) variance: examples zizou 2023-04-25 22:43

- total (pooled) variance: examples BEQool 2023-04-25 10:57

- total (pooled) variance: examples zizou 2023-04-22 21:06

- total (pooled) variance: examples BEQool 2023-04-22 18:20

- Higher-Order Crossovers Helmut 2023-04-20 10:19

- Parallel designs (total variance) Nav Coelho 2007-07-20 18:38
- Sample size estimation for parallel design Dipesh Jayswal 2007-07-24 08:52

- Parallel designs (total variance) Helmut 2007-07-20 16:29