We are given the following situation in the question:
"A statistics professor asked students in a class their ages. On the basis of this information, the professor states that the average age of all the students in the university is 21 years."
This is a n example of statistical Inference.
Statistical inference is the procedure of making inference or estimating parameters of a population with the help of test statistics.
In the given situation the university students are the population and the students of a particular class are sample.
The professor with the help of sample statistic (mean age of students in class) approximated the mean age of students in the university.
The answer is 2 y= total installation cost. x is the variable representing the number of months of service and $40 is the fixed price while $90 is dependent on the xvalue
