Both of these conditions must be true in order for the assumption that the binomial distribution is approximately normal. In other words, if and
then we can use a normal distribution to get a good estimate of the binomial distribution. If either np or nq is smaller than 5, then a normal distribution wouldn't be a good model to use.
side note: q = 1-p is the complement of probability p
The intensity of sound which the decibel level of the sound measures 156 is 3.981 × 10³ W/m²
Decibel level, dB = 10log₁₀(I/I₀) where dB = decibel level = 156, I = intensity at 156 dB and I₀ = 10⁻¹² W/m².
Since we require I, making I subject of the formula, we have
dB/10 = log₁₀(I/I₀)
Substituting the values of the variables into the equation, we have
I = 3981.072W/m²
I = 3.981 × 10³ W/m²
So, the intensity of sound which the decibel level of the sound measures 156 is 3.981 × 10³ W/m²
Learn more about intensity of sound here: