# probability distribution and SD of X

• March 22nd 2011, 10:13 PM
sanja85
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.
• March 22nd 2011, 10:50 PM
Sambit
$X\sim Bin(n=15,p=0.30)$. calculate the answers from this.
• March 30th 2011, 07:42 AM
sanja85
could you explain this to me, this is the first time im doing this :(
• March 30th 2011, 02:34 PM
mr fantastic
Quote:

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.