Sample Size Calculation for Longitudinal Analysis of Haemoglobin Concentration

Good morning all

I need assistance to calculate the minimum sample size for a piece of hospital-based research work.

The aim is to determine the appropriate time for the estimation of haemoglobin concentration after blood transfusion in children aged 1- 17 years.

With objectives to determine the time of equilibration of haemoglobin concentration after blood transfusion and to determine the relationship between time of equilibration and recipients’ variables like age, sex, and body mass index and pre-transfusion Hb concentration and To determine the relationship between donor’s Hb concentration, duration of storage of blood and equilibration time.

I wish to know what level of change occurs in haemoglobin concentration between 1, 6, 12, and 24 hours after a blood transfusion and so will be collecting blood samples at 1, 6, 12, and 24 hours

I suppose this is a time series or panel data and I am needed to show how I will derive the minimum sample size

I need to know how the formula to use to estimate the minimum sample size and how to calculate it manually

Thank you

Ezeanosike Obum