Suppose that n measurements are to be taken under a treatment condition and another n measurements are to be taken independently under a control condition. it is thought that the Standard deviation of a single observation is about 10 under both conditions. how large n should be so that the test of H0: mu_x=mu_y against the one sided alternative Ha: mu_x > mu_y has a power of 0.5 if mu_x-mu_y=2 and significant level = 0.1

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