We will have the following:
*There is a 1/3 chance for each question.
[tex]p=(19)(\frac{1}{3})\Rightarrow P=\frac{19}{3}\Rightarrow P\approx6.3[/tex]So, you should get about 6 answers correctly by guessing alone.
***We have that an unusual event is if the probability of it occurring is less than 5%. 2 in standard deviation is well greater than this, so it should not necessarily be considered unusual.
