In: Statistics and Probability
Assume there are 10 dogs , 5 great danes and 5 labs.
a. If the sampling is done with replacement what is the probability that the 3rd great dane selected is the 4th 5th or 6th dog selected?
b. do the same assuming its done without replacement
a)P( 3rd great dane selected is the 4th 5th or 6th dog selected)=P(2 out of first 3 are great dane and 4th is great dane)+P(2 out of first 4 are great dane and 5th is great dane)+P(2 out of first 5 are great dane and 6th is great dane)
=(3C2(0.5)2*(0.5))*0.5+(4C2(0.5)2*(0.5)2)*0.5+(5C2(0.5)2*(0.5)3)*0.5=0.53125
b)
P( 3rd great dane selected is the 4th 5th or 6th dog selected)=P(2 out of first 3 are great dane and 4th is great dane)+P(2 out of first 4 are great dane and 5th is great dane)+P(2 out of first 5 are great dane and 6th is great dane)
=(5C2*5C1/10C3)*(3/7)+(5C2*5C2/10C3)*(3/6)+(5C2*5C3/10C3)*(3/5)=(5/12)*(3/7)+(10/21)*(3/6)+(25/63)*(3/5) =0.654762