There is a maxim that goes: don't judge my life by the chapter you walked in on. When we violate this maxim, what kind of sample are we using (voluntary, random, convenience) ? Given that we are using that kind of sample, what mistakes are we liable to make? Describe a concrete scenario in which a person, because he/she violates this maxim, ends up misjudging another. Lastly, do you think that it is common or uncommon for people to violate this maxim?

You are using the random sample. If you meet Sally for the first time on a day that she is having a bad morning because she is running late she may be more snappy than usual. You should not judge her for this because it is not an accurate representation of her overall personality. Meeting her at that one moment in time when she was upset does not show how she is overall as a person. That is why people say a first impression is very important, but if you were to judge Sally for being snappy and you decided that she did not like her from that moment forward you could be missing out on having a good new friend.