Scatter Plots and Correlation Relationships

Which of the following correlation coefficients indicates the strongest relationship between variables?

• -0.95

• 0.30

• 0.50

• 0.90

Which of the following shows the least correlation between two variables?

• -0.99

• -0.25

• 0

• 0.99

Which of the following values could not represent a correlation coefficient?

• r =0.99

• r = 1.09

• r = -0.73

• r = -1.0

Which data will most likely show a negative correlation when graphed on a scatter plot?

• The student’s height and their general average.

• The outside temperature and the number of people wearing jackets.

• The number of visitors at an amusement park and the length of the lines for the rides.

• The distance a student lives from school and the amount of time it takes to get to school.

It is found that there is a correlation of exactly 1.0 between two variables. Which of the following is INCORRECT?

• Correlation is measured on a scale of −1.0 to 1.0.

• The association between the two variables is positive.

• There is a strong association between the two variables.

• There is enough evidence to assert that one variable causes the other.

Which scatter plot shows most likely a positive correlation?

• I only

• II only

• Both I and II

• Neither

In a medical school, it is found that there is a correlation of −0.95 between the amount of coffee consumed by students and the number of hours students sleep each night. Which of the following is TRUE?

i. There is a positive association between the two variables.

ii. There is a strong correlation between the two variables.

iii. Coffee consumption in medical school students causes students to sleep less each night.

• ii only

• iii only

• i and ii

• i and iii

The coefficient correlation r between two bivariate data is -0.9, which best describes the correlation?

• The strength of correlation is negligible.

• The correlation is very low but negative.

• The correlation is very high but negative.

• There is no correlation because the computed r is negative.

The scatter plot shows the number of absences in a week for classes of different sizes. Mark concluded that there is a positive correlation between class size and the number of absences. Which statement best describes why Trevor’s conclusion was incorrect?

• The largest class does not have the most absences.

• The smallest class does not have the least number of absences.

• The data show no relationship between class size and number of absences.

• The data show a negative relationship between class size and the number of absences.

The coaches of a group of debate teams answered a survey about hours of debate, team practice and number of team wins. The given graph shows the results of the survey.The scatterplot indicates which of the following?

• A positive correlation

• A negative correlation

• No correlation

• A parallel correlation