The question is:

Broken arms can be treated with surgery or splints. In a study with 200 patients, half had surgery and half used splints. In the surgery group, 80 patients showed improvement after 2 months whilst 50 who used splints improved. Is surgery more effective than splints for improvement?

a) Write appropriate hypotheses.
b) Test the hypothesis, find the P-value and state your conclusion. Use α = 0.025.
c) Create a 95% confidence interval for the difference in improvement rates, and interpret your interval.

a) Ho: Psurgery - Psplints = 0
Ha: Psurgery - Psplints > 0

Is a right? and for b, I don't know which formula to apply because I initially used the pooled formula, but because the data is halved, n1 and n2 are both equal and I'm not sure if that is right...