To determine how many times Jenna should expect to pull a yellow marble after drawing a marble 15 times, we first need to find the probability of drawing a yellow marble in one draw.
Jenna's bag contains:
- 2 blue marbles
- 2 red marbles
- 2 yellow marbles
In total, there are \( 2 + 2 + 2 = 6 \) marbles in the bag.
The probability \( P \) of drawing a yellow marble in one draw is given by the formula:
\[ P(\text{yellow}) = \frac{\text{number of yellow marbles}}{\text{total number of marbles}} = \frac{2}{6} = \frac{1}{3} \]
Now, if Jenna draws a marble 15 times, the expected number of times she will pull a yellow marble can be calculated using the formula for the expected value:
\[ \text{Expected value} = \text{number of trials} \times P(\text{yellow}) \]
Substituting the values we have:
\[ \text{Expected value} = 15 \times \frac{1}{3} = 5 \]
Therefore, Jenna should expect to pull a yellow marble \( \boxed{5} \) times.