(i) To find \(\sigma\), we use the standard normal distribution. The probability that \(X > 0\) is 0.25, which corresponds to a \(z\)-value of 0.674 (since the probability to the right of the mean is 0.25).

Using the standardization formula:

\(z = \frac{0 - (-3)}{\sigma} = 0.674\)

Solving for \(\sigma\):

\(\sigma = \frac{3}{0.674} \approx 4.45\)

(ii) The probability that a single value of \(X\) is positive is 0.25. We need to find the probability that fewer than 2 out of 8 values are positive. This is a binomial distribution problem with \(n = 8\) and \(p = 0.25\).

We calculate \(P(0) + P(1)\):

\(P(0) = (0.75)^8\)

\(P(1) = \binom{8}{1} (0.25)(0.75)^7\)

\(P(0) + P(1) = 0.1001 + 0.2670 = 0.367\)