A five person science club is chosen at random from five girls and fifteen boys. Conditioned on there being at least 1 girl on the club, what is the expected number of boys?
Contingency Table
A contingency table can be defined as the visual representation of the relationship between two or more categorical variables that can be evaluated and registered. It is a categorical version of the scatterplot, which is used to investigate the linear relationship between two variables. A contingency table is indeed a type of frequency distribution table that displays two variables at the same time.
Binomial Distribution
Binomial is an algebraic expression of the sum or the difference of two terms. Before knowing about binomial distribution, we must know about the binomial theorem.
A five person science club is chosen at random from five girls and fifteen boys. Conditioned on there being
at least 1 girl on the club, what is the expected number of boys?
We make a table using the given information.
| Possible cases | Number of boys (xi) | number of cases | probability(pi) |
| 1 girl, 4 boy | 4 | (5C1)(15C4)= | |
| 2 girls, 3 boys | 3 | (5C2)(15C3)= | |
| 3 girls, 2 boys | 2 | (5C3)(15C2)=050 | |
| 4 girls, 1 boys | 1 | (5C4)(15C1)=75 | |
| 5 girls, 0 boys | 0 | (5C5)(15C0)=1 | |
| Total | 12501 | 1 |
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