Animals were randomly divided into 4 groups by a research assistant blind to the experiments. To determine the sample size, we set a power value of around 90%, and we also determined the direction of the effect as two tailed with α level = 0.05, δ mean = 1.2, σ2 = 0.64, and attrition around 1%. We then calculated the sample size using the following formula: N = 2σ2(Zα + Z1 − β)2/(μ1 − μ2)2 = 9.33.
Note: σ2 = 0.64; (μ1 − μ2)2 = δ mean = 1.2; Zα = 1.96; Z1 − β = 1.28, which were determined by a standard normal distribution table.
The corrected sample size = sample size/(1% attribution of animal) = 9/0.9 = 10. However, statistical significance was observed with 9 pups, so we used only 9 rat pups for each group in this experiment. Eight rats were treated with 0.2 mg/kg L-thyroxin (T4; Sigma, Kawasaki, Japan) (HI+low T4 group), 9 rats were administered 1 mg/kg T4 (HI+high T4 group), and 9 animals were injected with normal saline (NS). T4 or NS was injected intraperitoneally 48 to 96 h after hypoxia. Eight pups received a sham operation (sham controls). While T4 treatment reduced body weight, there was no significant difference between groups on postnatal day (P) 7, P9, and P11.
Note: σ2 = 0.64; (μ1 − μ2)2 = δ mean = 1.2; Zα = 1.96; Z1 − β = 1.28, which were determined by a standard normal distribution table.
The corrected sample size = sample size/(1% attribution of animal) = 9/0.9 = 10. However, statistical significance was observed with 9 pups, so we used only 9 rat pups for each group in this experiment. Eight rats were treated with 0.2 mg/kg L-thyroxin (T4; Sigma, Kawasaki, Japan) (HI+low T4 group), 9 rats were administered 1 mg/kg T4 (HI+high T4 group), and 9 animals were injected with normal saline (NS). T4 or NS was injected intraperitoneally 48 to 96 h after hypoxia. Eight pups received a sham operation (sham controls). While T4 treatment reduced body weight, there was no significant difference between groups on postnatal day (P) 7, P9, and P11.