PSYC1111 Study Guide - Final Guide: Genitive Case, Negative Relationship, Scatter Plot
Displaying Bivariate Numerical Data: Scatterplots
• Does height influence artistic score?
Bivariate Data
• measurements or observations on two variables, x and y
• when both x and y are numerical variable, each observation consist of a pair of
numbers; the first number in a pair is the value of x, and the second number is the
value of y
find more resources at oneclass.com
find more resources at oneclass.com
Example 2: Smoking and lung cancer
• Smoking index
o Number of cigarettes per day
o 100 average
• Mortality index is standardised mortality ratio for deaths from lung cancer
o 100 average
• If mortality index is greater than 100, more deaths from lung cancer than would be
expected
• If less than 100 fewer deaths from lung cancer than expected
Correlation Scatterplot
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Example 2: smoking and lung cancer: smoking index, number of cigarettes per day, 100 average, mortality index is standardised mortality ratio for deaths from lung cancer, 100 average. If mortality index is greater than 100, more deaths from lung cancer than would be expected. If less than 100 fewer deaths from lung cancer than expected. Positive relationship: variables tend to change in same direction, x increases y increases, x decreased y decreases. Negative relationship: variables tend to change in the opposite direction, as x increases y decreases, as x decreases y increases. No linear relationship: change in one variable not correlated with change in other. The pearson correlation r is sensitive only to linear relationships: the two variables graphed below are related, but the relationship is not linear. The correlation coefficient (r) calculated for this data set would be close to zero.
