/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 57 The article "Behavioural Effects... [FREE SOLUTION] | 91Ó°ÊÓ

91Ó°ÊÓ

The article "Behavioural Effects of Mobile Telephone Use During Simulated Driving" (Ergonomics, 1995: 2536-2562) reported that for a sample of 20 experimental subjects, the sample correlation coefficient for \(x=\) age and \(y=\) time since the subject had acquired a driving license (yr) was \(.97\). Why do you think the value of \(r\) is so close to 1 ? (The article's authors give an explanation.)

Short Answer

Expert verified
The correlation is strong because as age increases, the years since acquiring a license also increase nearly proportionally.

Step by step solution

01

Understand Correlation Coefficient

The sample correlation coefficient, denoted as \(r\), measures the strength and direction of a linear relationship between two variables. In this context, it is the correlation between the age of the driver (\(x\)) and the years since the driving license was acquired (\(y\)). A value of \(r = 0.97\) indicates a very strong positive linear relationship.
02

Analyze Variables Relationship

Consider the variables: age and time since acquiring a driving license. These variables are naturally related because age is primarily determined by the time since licenses are given at a specific minimum age threshold, and people continue to age linearly with time.
03

Reasoning Behind the High Correlation

The high correlation of \(r = 0.97\) suggests that as age increases, the years since acquiring a license also increase almost in direct proportion. This logical relationship exists because individuals typically acquire a driver's license during their late teenage years and all subsequent years contribute to both their total age and years with a license incrementally.
04

Conclusion

The strong relationship is due to their linear dependency. This large coefficient indicates that both age and years since acquiring the license grow together; therefore, it's expected that their correlation is near absolute, reflecting their temporal connection and growth over time.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Linear Relationship
In statistical terms, a linear relationship indicates a direct, proportional connection between two variables. When you plot these variables on a graph, if they exhibit a linear relationship, the points will form a straight line.
Understanding the extbf{correlation coefficient}, denoted as \( r \), is crucial here. This value ranges from -1 to 1 and measures how closely the data points fit a straight line. An \( r \) value of 1 or -1 reflects a perfect linear relationship, either positive or negative.
A value of 0 means no linear relationship.
  • A positive \( r \), like 0.97, implies that as one variable increases, the other one does as well.
  • Conversely, a negative \( r \) would imply inversion, where an increase in one variable would correspond to a decrease in the other.
In our context, \( r = 0.97 \) indicates a very strong positive linear relationship between age and time since acquiring a license, implying these two factors grow together in an almost consistent path as people age.
Age and License Acquisition
Age and the time since acquiring a driving license are closely connected. Typically, individuals receive their licenses during adolescence.
This start point creates a baseline age from which years with the license can grow. Given the legal minimum age for acquiring a license leads to a logical and predictable relationship between these two variables.
  • Young adults begin driving around the same age due to legal constraints.
  • Once licensed, each additional year adds equally to both their age and their time with the license.
This linear growth pattern explains how age and license acquisition are tied. It emphasizes why there's often a strong linear relationship between the two, reflecting consistent and predictable human development stages.
Positive Correlation
The concept of a positive correlation involves both variables moving in the same direction. In the case of age and years since license acquisition, a positive correlation shows that as individuals age, the time since they obtained their license increases too.
  • A strong positive correlation, like 0.97, suggests a near-perfect direct relationship.
  • It means both variables increase together, reinforcing the idea of consistent growth.
This is expected between age and license holding time because, naturally, as one gets older, the count of years since obtaining their driving license rises. This correlation reinforces the common sense understanding of how people age and how such life milestones are marked together over the years.

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Most popular questions from this chapter

Suppose an investigator has data on the amount of shelf space \(x\) devoted to display of a particular product and sales revenue \(y\) for that product. The investigator may wish to fit a model for which the true regression line passes through \((0,0)\). The appropriate model is \(Y=\beta_{1} x+\epsilon\). Assume that \(\left(x_{1}, y_{1}\right), \ldots,\left(x_{n}, y_{n}\right)\) are observed pairs generated from this model, and derive the least squares estimator of \(\beta_{1}\).

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Consider the following three data sets, in which the variables of interest are \(x=\) commuting distance and \(y=\) commuting time. Based on a scatter plot and the values of \(s\) and \(r^{2}\), in which situation would simple linear regression be most (least) effective, and why? $$ \begin{array}{lllrrrrr} \text { Data Set } & & 1 & & & 2 & & 3 \\ \hline & \boldsymbol{x} & \boldsymbol{y} & \boldsymbol{x} & \boldsymbol{y} & \boldsymbol{x} & \boldsymbol{y} \\ & 15 & 42 & 5 & 16 & 5 & 8 \\ & 16 & 35 & 10 & 32 & 10 & 16 \\ & 17 & 45 & 15 & 44 & 15 & 22 \\ & 18 & 42 & 20 & 45 & 20 & 23 \\ & 19 & 49 & 25 & 63 & 25 & 31 \\ & 20 & 46 & 50 & 115 & 50 & 60 \\ \hline \end{array} $$

The article "Increases in Steroid Binding Globulins Induced by Tamoxifen in Patients with Carcinoma of the Breast" \((J\). of Endocrinology, 1978: 219-226) reports data on the effects of the drug tamoxifen on change in the level of cortisol-binding globulin (CBG) of patients during treatment. With age \(=x\) and \(\Delta \mathrm{CBG}=y\), summary values are \(n=26\), \(\sum x_{i}=1613, \sum\left(x_{i}-\bar{x}\right)^{2}=3756.96, \sum y_{i}=281.9\) \(\sum\left(y_{i}-\bar{y}\right)^{2}=465.34\), and \(\sum x_{i} y_{i}=16,731\) a. Compute a \(90 \%\) CI for the true correlation coefficient \(\rho\). b. Test \(H_{0}: \rho=-.5\) versus \(H_{\mathrm{a}}: \rho<-.5\) at level \(.05\). c. In a regression analysis of \(y\) on \(x\), what proportion of variation in change of cortisol-binding globulin level could be explained by variation in patient age within the sample? d. If you decide to perform a regression analysis with age as the dependent variable, what proportion of variation in age is explainable by variation in \(\triangle \mathrm{CBG}\) ?

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