Answer: Required mean would be 15.
Step-by-step explanation:
Since we have given that
Number of girls G= 75
Number of boys B= 100
Probability that girls smoke = P₂ = 0.20
Probability that girls don't smoke = P'₂=1-0.20=0.80
Probability that boys smoke = P₁ = 0.30
Probability that boys don't smoke = P'₁=1-0.30=0.70
We need to find the mean of the sampling distribution of the difference in the sample proportion of girl smokers and boys smokers.
So, it becomes,
Hence, required mean would be 15.