In a survey, 162 respondents say that they never use a credit card, 1223 say that they use it sometimes, and 2831 say that they use it frequently. what is the probability that a randomly selected person uses a credit card frequently? is it unlikely for someone to use a credit card frequently? how are all of these results affected by the fact that the responses were obtained by those who decided to respond to a survey posted on the internet?
the probability that a randomly selected person uses a credit card frequently is

162 = never use a credit card
1223 = use credit card sometimes
2831 = use a credit card frequently

Probability that a randomly selected person uses a credit card frequently:
1223 / 162 + 1223 + 2831
1223 / 4216
As a percentage, this is about a 29 percent chance. I guess you could say it's unlikely, because the probability is only 29 percent. 

The fact that the survey was taken on the internet means it's not really a reliable survey, because only those who have access to the internet would be able to take the survey, which rules out a good group of people.