To determine how many times Daria should expect to pull a yellow marble in the next 50 trials, we first need to find the probability of pulling a yellow marble based on her initial experiment.
The total frequency of marbles pulled in Daria's initial experiment is:
\[ 26 \text{ (yellow)} + 34 \text{ (green)} + 18 \text{ (purple)} + 22 \text{ (red)} = 100 \]
Next, we calculate the probability of pulling a yellow marble:
\[ P(\text{yellow}) = \frac{\text{Frequency of yellow}}{\text{Total frequency}} = \frac{26}{100} = 0.26 \]
Now, we can use this probability to estimate how many yellow marbles she should expect to pull in 50 more trials:
\[ \text{Expected number of yellow marbles} = P(\text{yellow}) \times \text{Number of trials} = 0.26 \times 50 = 13 \]
Thus, Daria should expect to pull a yellow marble approximately 13 times.