Answer:
a) Probability that exactly 29 of them are spayed or neutered = 0.074
b) Probability that at most 33 of them are spayed or neutered = 0.66
c) Probability that at least 30 of them are spayed or neutered = 0.79
d) Probability that between 28 and 33 (including 28 and 33) of them are spayed or neutered = 0.574
Step-by-step explanation:
This is a binomial distribution question
probability of having a spayed or neutered dog, p = 0.67
probability of having a dog that is not spayed or neutered, q = 1 - 0.67
q = 0.23
sample size, n = 48
According to binomial distribution formula:
![P(X=r) = nCr p^r q^{n-r}](https://tex.z-dn.net/?f=P%28X%3Dr%29%20%3D%20nCr%20p%5Er%20q%5E%7Bn-r%7D)
where ![nCr = \frac{n!}{(n-r)! r!}](https://tex.z-dn.net/?f=nCr%20%3D%20%5Cfrac%7Bn%21%7D%7B%28n-r%29%21%20r%21%7D)
a) Probability that exactly 29 of them are spayed or neutered
![P(X= 29) = 48C29 * 0.67^{29} * 0.23^{19}\\P(X=29) = 0.074](https://tex.z-dn.net/?f=P%28X%3D%2029%29%20%3D%2048C29%20%2A%200.67%5E%7B29%7D%20%2A%200.23%5E%7B19%7D%5C%5CP%28X%3D29%29%20%3D%200.074)
b) Probability that at most 33 of them are spayed or neutered
![P(X \leq 33) =1 - P(X > 33)\\P(X \leq 33) =1 - 0.34\\P(X \leq 33) = 0.66](https://tex.z-dn.net/?f=P%28X%20%5Cleq%2033%29%20%3D1%20-%20%20P%28X%20%3E%2033%29%5C%5CP%28X%20%5Cleq%2033%29%20%3D1%20-%200.34%5C%5CP%28X%20%5Cleq%2033%29%20%3D%200.66)
c) Probability that at least 30 of them are spayed or neutered
![P(X \geq 30) = 1 - P(x < 30)\\P(X \geq 30) = 1 - 0.21\\P(X \geq 30) = 0.79](https://tex.z-dn.net/?f=P%28X%20%5Cgeq%2030%29%20%3D%201%20-%20P%28x%20%3C%2030%29%5C%5CP%28X%20%5Cgeq%2030%29%20%3D%201%20-%200.21%5C%5CP%28X%20%5Cgeq%2030%29%20%3D%200.79)
d) Probability that between 28 and 33 (including 28 and 33) of them are spayed or neutered.
![P(28 \leq X \leq 33) = P(X=28) + P(X=29) + P(X=30) + P(X=31) + P(X=32) + P(X=33)\\P(28 \leq X \leq 33) = 0.053 + 0.074 + 0.095 + 0.112 + 0.121 + 0.119\\P(28 \leq X \leq 33) = 0.574](https://tex.z-dn.net/?f=P%2828%20%5Cleq%20X%20%5Cleq%2033%29%20%3D%20P%28X%3D28%29%20%2B%20P%28X%3D29%29%20%2B%20P%28X%3D30%29%20%2B%20P%28X%3D31%29%20%2B%20P%28X%3D32%29%20%2B%20P%28X%3D33%29%5C%5CP%2828%20%5Cleq%20X%20%5Cleq%2033%29%20%3D%200.053%20%2B%200.074%20%2B%200.095%20%2B%200.112%20%2B%200.121%20%2B%200.119%5C%5CP%2828%20%5Cleq%20X%20%5Cleq%2033%29%20%3D%200.574)