Exam 8: Regression Wisdom

Two variables that are actually not related to each other may nonetheless have a very high correlation because they both result from some other, possibly hidden, factor.This is an Example of

A residual plot that has no pattern is a sign that…

Linear regression was used to describe the trend in world population over time.Below is a plot of the residuals versus predicted values.What does the plot of residuals suggest?

When using midterm exam scores to predict a student's final grade in a class, the student would prefer to have a

Another farmer has increased his wheat production by about the same percentage each year. His most useful predictive model is probably…

Over the past decade a farmer has been able to increase his wheat production by about the same number of bushels each year.His most useful predictive model is probably…

Which of the following is not a goal of re-expressing data?

Which statement about residuals plots is true? I.A curved pattern indicates nonlinear association between the variables. II)A pattern of increasing spread indicates the predicted values become less reliable as the Explanatory variable increases. III)Randomness in the residuals indicates the model will predict accurately.

Which of the following is not a source of caution in regression between two variables?

The $\sqrt { \text { str } } = 12 + 20 ($ dia $)$ can be used to predict the breaking strength of a rope (in pounds) from its diameter (in inches). According to this model, how much force should a rope onehalf inch in diameter be able to withstand?

Which statement about re-expressing data is not true? I.Unimodal distributions that are skewed to the left will be made more symmetric by taking The square root of the variable. II)A curve in which the direction of the association changes from negative to positive will Not benefit from re-expression. III)One goal of re-expression may be to make the variability of the response variable more Uniform.

A scatterplot of log(Y) vs.log(X) reveals a linear pattern with very little scatter.It is probably true that …

If a data point is influential it…

A residuals plot is useful because I.it will help us to see whether our model is appropriate. II)it might show a pattern in the data that was hard to see in the original scatterplot. III)it will clearly identify influential points.

Which is true? I. Random scatter in the residuals indicates a model with high predictive power. II. If two variables are very strongly associated, then the correlation between them will be near $+ 1.0$ or $- 1.0$ . III. The higher the correlation between two variables the more likely the association is based in cause and effect.

Which statement about correlation is true? I.Regression based on data that are summary statistics tends to result in a higher Correlation. II)If r = 0.95, the response variable increases as the explanatory variable increases. III)An outlier always decreases the correlation.

The model $\sqrt { \text { distance } } = 3.30 + 0.235$ (speed. can be used to predict the stopping distance (in feet. for a car traveling at a specific speed (in mph.) According to this model, about how much distance will a car going $65 \mathrm { mph }$ need to stop?