# Thread: probability distribution and SD of X

1. ## probability distribution and SD of X

Phenylthiocarbamide, or PTC, is a molecule that tastes very bitter to those who can taste it. However, about 30% of people cannot taste it, due to a recessive allele in their DNA. Assume that the proportion with this genetic trait is exactly 30%. A researcher administers PTC to 15 randomly-selected subjects. Let X be the number of these subjects who are able to taste PTC.

(a) What is the probability distribution of X?

(b) Calculate:

(i) the mean and standard deviation of X.
(ii) P( X > 6)
(iii) P( 3 ≤ X ≤ 7)

(c) If 10 of the subjects could taste PTC, would this be an unusual sample? Justify your answer.

2. $X\sim Bin(n=15,p=0.30)$. calculate the answers from this.

3. could you explain this to me, this is the first time im doing this

4. Originally Posted by sanja85
could you explain this to me, this is the first time im doing this
You have been told exactly what to do. Now you clearly need to go back to your class notes and textbook and reviewthe Binomial probability distribution.