Answer to Question 1
Pearson Product Moment correlation coefficients are the most commonly reported correlations and are designated as r. They range from an anchor point of -1.0 to immediately below 0 for negative correlations, and from immediately above 0 to an anchor point of +1.0 for positive correlations. An r = 0 indicates the absence of a relationship. The absolute value of the correlation coefficient indicates the strength of the relationship and the sign indicates the nature of the relationship.
Answer to Question 2
Correlational studies (also called observational studies) describe the magnitude of covariation between stress and illness but do not give sufficient information to determine causation. In other words, they only give us information about the nature and strength of the relationship and not its causal relations. Correlation coefficients may be used to summarize the relationship between variables found in correlational studies.
Intradermal drug administration: (a) cross section of skin showing depth of needle insertion Source:
Product & Process Influences - Sterile Products
Product Rule
Use the product rule to find derivative
Find derivative using product rule
The phenotype of an organism is the product of interactions