The normal distribution can be used as an approximation of a binomial distribution under the following conditions:
- \( np \geq 10 \)
- \( n(1-p) \geq 10 \)
These conditions ensure that both the number of successes and the number of failures are sufficiently large, which makes the binomial distribution more closely resemble a normal distribution. If either condition is not met, the normal approximation may not be very accurate.