A conditional probability is the chance of an event when you already know the selection comes from a particular group. In a two-way table, use that group’s row or column total as the denominator, then find the cell where that group and the target meet. Dividing by the full-table total ignores the condition.
Hints
- Hint 1
A condition tells you which orders can still be selected. The chosen order is already known to have paid gift-wrap. Which column total counts only orders that could be picked?
- Hint 2
A two-way table sorts orders by two traits. Find where the gift-wrapped column and express-shipping row meet. How does that count compare with the total number of gift-wrapped orders?
Step-by-step
Restrict the group, then divide
Step 1Find the group that can be selected
The order is already known to include paid gift-wrap. So the gift-wrapped column becomes the whole group: its total is orders, not all orders.
- Step 2
Find the express orders in that group
The express-shipping row and gift-wrapped column meet at . That’s the favorable count: the gift-wrapped orders that also had express shipping.
- Step 3
Write the probability
For a conditional probability, divide the favorable count by the total in the group you can pick from: . The bar means “given that” the order was gift-wrapped.
- Step 4
Compare the decimal with the choices
Type into Desmos. It shows , which is closest to . So the probability that a selected gift-wrapped order had express shipping is closest to . Choice C.