Does vitamin C prevent colds? Vitamin C was given to [6]

a random sample of 130 skiers and a placebo has another sample

aleatory of 128 skiers. During the last winter season, 30 of the skiers

who had been given vitamin C and 39 of those who had received

placebo got colds.

(a) At the threshold of 0.05, can we conclude that vitamin C significantly reduces the risk of contracting colds? to answer the question,

calculate a confidence interval.

(b) Do you come to the same conclusion, at the threshold of 0.10? Explain.