Correlation and R Value Review

If a data set has an r-value of 0.687, then how would you describe the correlation?

• Very weak

• Weak

• Moderate

• Strong

Answer explanation

The r-value is between 0.5 and 0.75 which is the moderate range for r-values.

If a data set has a r-value of zero, then what does this mean?

• There is no data.

• The correlation is very weak.

• The correlation is very strong.

• There is no correlation.

Describe the correlation for the table.

• Moderate Negative

• Strong Positive

• Strong Negative

• Perfect Negative

Answer explanation

r = -0.995

Find r and round to the nearest thousandth.

• 0.4806

• 0.48

• 0.481

• 0.480

Answer explanation

The number after the 0 is a 6 which rounds up.

Remove the outlier from the data set and calculate the r-value.

• 1

• -1

• 0

• There is no r-value.

Which statement accurately describes the effect outliers have on the correlation of a data set?

• The outliers have no effect on the correlation.

• The outliers affect whether the data set has a positive or negative correlation.

• The outliers affect the strength of the correlation.

• The outliers affect whether the correlation is linear or non-linear.

Answer explanation

The outliers definitely affect the correlation of a data set. The outliers will not cange the correlation from positive to negative or linear to non-linear, but they can affect the strength. An outlier may cause the correlation to be not as strong as it should be if there was no outlier.

The correlation of a data set is represented by r = 0.267. How would you describe the correlation?

• Very weak

• Weak

• Moderate

• Strong

Answer explanation

Any r-value between 0.25 and 0.5is considered a weak correlation.

Describe the correlation for a r-value of -0.58

• Very weak

• Weak

• Moderate

• Strong

Answer explanation

Any r-value with an absolute value between 0.5 and 0.75 is considered moderate.

True or False. Nadia found the r-values for two data sets. One data set had a r-value of -0.345 and the other had a r-value of 0.345. She is confused because the graphs look different but she likes they should look the same. Is this true?

• This is true because the absolute value of the r-values are the same.

• This is false because the absolute value of the r-values are the same.

• This is true because the one graph is negative and one graph is positive.

• This is false because the one graph is negative and one graph is positive.

Describe the correlation for the data set.

• Strong & Negative

• Weak & Negative

• No correlation

• Strong & Positive

Answer explanation

r = -0.986