(Exercises 1326) For each description of data, identify the Ws, name the variables, specify for each variable whether its use indicates that it should be treated as categorical or quantitative, and, for any quantitative variable, identify the units in which it was measured (or note that they were not provided).Streams In performing research for an ecology class, students at a college in upstate New York collect data on local streams each year. They record a number of biological, chemical, and physical variables, including the stream name, the substrate of the stream (limestone, shale, or mixed), the acidity of the water (pH), the temperature (C), and the BCI (a numerical measure of biological diversity).

Conditional Probability: probability of an event, given that another event has occurred P(A| B) is the probability of A, given that B has occurred P(A| B) is not the same as P(B|A) If events are independent then P(A)=P(A|B) and P(B)=P(B|A) A contingency table (two way table) is a visual representation of the relationships between the variable. They make probabilities easier to figure out. Levels of the explanatory variables are the rows of the table and response variables are the columns Risk=Number in category/Total number in group We can use a contingency table to calculate Relative Risk= risk in category 1/ risk in category 2 Baseline risk Percent change in risk= (relative risk – 1) 100% Positive means risk increases Negative means risk decreases If relative risk is 1 then the