A study randomized children aged 5 to 12 to either a new intervention for higher calcium levels or to standard care (16 per group). The mean increase in calcium levels for the intervention group was 978 with a standard deviation of 313. In the control group the mean change was 773 with a standard deviation of 268.

a) What is the rejection region for this test? (df=n1+n2-2)

b) Test ata=0.05 if there is a statistically significant difference in mean change in calcium levels between the two study groups.