Identify a potential source of bias (if any). Using random digit dialing, 1599 people were called and asked what obstacles (such as childcare) kept them from exercising. (Source: Yankelovich Partners, Inc. for Shape Up America!)

Suppose you are analyzing the relationship between time and distance given in a table,and there are 4 values for each quantity.you divide distance 2 minus distance 1 by time 2 minus time 1.you then divide distance 4 minus distance 3 by time 4 minus time 3 and get a different answer.what can you say about the relationship?