Now we want to know if the IQ of students at a small private University in Pennsylvania differs from that of the general population. Instead of testing all the University students we randomly select a sample of 30 students.
Any observed difference is simply the result of sampling error.
The the mean of the population that the sample is drawn from is not 100. The conventional significance level is .05. The above example is a Nondirectional hypothesis. That is, we are interested in knowing if the IQ scores differ but we do not make any statements in regards to whether the IQ score will be higher or lower. The hypothesis would be directional if we had stated that IQ scores of college students are typically higher then the general population average.