An anchoring bias occurs when you focus on

An anchoring bias occurs when you focus on one piece of information versus all of the information
For example, you never met mr. Kirk your close friend told you that Mr.Kirk is a liar that should not be tasted (even though your friend offer no proof).
When you met Mr.Kirk personally, you will have a basic assumption that Mr.Kirk is a liar no matter what other qualities that he may conveyed

Number of members chosen by Helena in her homeroom = 5

Mean number of tickets = 16

So, total candidates who had purchased ticket = 16 × 5= 80

Now, number of candidates chosen randomly = 10

So, total candidates who had purchased ticket = 22.5 × 10=225

No, one sample can't be a better representation by choosing randomly a group of members.

In Sample 1 , we are considering only 5 drama numbers.

And In Sample 2, we are considering 10 random samples among 75 members.

The mean in two cases varies by (22.5-16=6.5) which is large because we are considering number of tickets sold by members of club.

It would have been better if she has taken more than 3 random samples of 15  students ,among 75 students, then she would have got appropriate mean or value near the mean.