The Wechsler Adult Intelligence Scale (IQ test) is constructed so that Full Scale IQ scores follow a normal distribution, with a mean of 100, and a standard deviation of 15. Dr.Smartyskirt is a University professor and believes that university professors are smarter than the national average and wants to use it (the intelligence of the professors) as a marketing tool to bring new students to the University.A researcher is hired to conduct a study to determine whether University professors, on average, have higher Full Scale IQs than the population. A random sample of 100 professors from various Universities were given the IQ test and were found to have an average Full Scale IQ of 140.

What is the value of the test statistic used to determine whether the mean Full Scale IQ score of the University professors is higher than the national average?

26.67

-26.67

2.67

-2.67