On the third day of Statistics, my teacher gave to me….three French hens. Because she is in a hurry, she randomly selects three pets from the local pet store. Find the probability that she selected three French hens.

Hens Chickens

French 10 20

American 30 40
In order to receive credit, you must show correct formula, substitution and final answer

3 answers

Use the Chi-square (X^2) method.

X^2 = ∑ (O-E)^2/E, where O = observed frequency and E = expected frequency.

∑ = sum of all the cells.

E = (column total * row total)/grand total

df = n - 1, where n = number of cells

Look up value in X^2 table in the back of your textbook.
I found the chi-square table, what would I put for the number of cells ? Im a little lost thanks :)
How many squares do you have in your Chi-square?