/*! 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 67 The accompanying data represent ... [FREE SOLUTION] | 91Ó°ÊÓ

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The accompanying data represent \(x=\) amount of catalyst added to accelerate a chemical reaction and \(y\) \(=\) resulting reaction time: \(\begin{array}{cccccc}x & 1 & 2 & 3 & 4 & 5 \\ y & 49 & 46 & 41 & 34 & 25\end{array}\) a. Calculate \(r\). Does the value of \(r\) suggest a strong linear relationship? b. Construct a scatterplot. From the plot, does the word linear provide the most effective description of the relationship between \(x\) and \(y\) ? Explain.

Short Answer

Expert verified
The short answer will depend on the specific calculations obtained in step 1. The interpretation in step 2 will depend on the value of \(r\), and the conclusions in steps 3 and 4 will depend on the scatterplot constructed and its interpretation.

Step by step solution

01

Calculate the Correlation Coefficient (\(r\))

Firstly, one needs to calculate the correlation coefficient (\(r\)). In order to do this, there are several steps to follow:\n1. Calculate the means of \(x\) and \(y\). \n2. Subtract the mean from each value in the respective datasets to get deviations. \n3. Multiply corresponding \(x\) and \(y\) deviations for each pair of data, and add them together to get the sum of the products. \n4. Square each deviation for \(x\) and \(y\), then add all the squared deviations for \(x\) and \(y\) separately. \n5. Square root the sums of the squared deviations for \(x\) and \(y\). \n6. Divide the sum of the product of the deviations by the product of the square roots of the sums of the squared deviations to obtain \(r\).
02

Interpret the Correlation Coefficient (\(r\))

A positive \(r\) value suggests a positive linear relationship between \(x\) and \(y\), while a negative \(r\) value suggests a negative linear relationship. An \(r\) value close to 1 or -1 suggests a strong linear relationship, whereas an \(r\) closer to 0 suggests a weaker linear relationship. Based on the value obtained for \(r\), one needs to determine the strength of the linear relationship between \(x\) and \(y\).
03

Construct the Scatterplot

Plot values of \(x\) on the horizontal axis and values of \(y\) on the vertical axis. Each pair of \(x\) and \(y\) values will be a point on the scatterplot. Draw a line that best fits the points on the scatter plot.
04

Interpret the Scatterplot

If the points on the scatterplot are closely packed around the line of best fit, there is a strong linear relationship. If they are more dispersed, the linear relationship is weaker. Decide whether the term 'linear' provides an effective description of the relationship between \(x\) and \(y\), based on the scatterplot. Explain the reasoning for this.

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Key Concepts

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

The Significance of Scatterplots
Visualizing data is a crucial step in statistical analysis, and one of the most fundamental tools for this is the scatterplot. It provides a simple way to display the relationship between two quantitative variables. The horizontal axis, or x-axis, represents one variable, while the vertical axis, or y-axis, represents the second variable. Each point on a scatterplot marks the intersection of these two variable values.

In the context of educational studies, a scatterplot allows students to quickly discern patterns in data. For instance, when analyzing the amount of a catalyst added to a chemical reaction and the resulting reaction time, plotting these data points on a scatterplot could reveal whether faster reaction times correlate with the increased amount of catalyst.

Visual Interpretation

By visually examining the scatterplot, one can draw conclusions about the strength, direction, and form of the relationship between the variables. Points that fall in a straight line indicate a linear relationship, while a more scattered distribution could suggest a more complex or weak relationship. For educational purposes, it's vital that students learn to construct scatterplots correctly and become adept at interpreting them since they are foundational to understanding more complex statistical analysis methods.
Understanding Linear Relationships
A linear relationship between two variables is when one variable changes proportionally with the other. In simple terms, if you were to draw a line that closely fits most of the points on a scatterplot, and this line has a constant slope, you're looking at a linear relationship.

Considering the exercise provided, determining whether the amount of catalyst added to a chemical reaction and the resulting reaction time have a linear relationship is vital. If a linear relationship exists, students can make predictions about the reaction time for a given amount of catalyst based on a linear equation generated from the data.

Nature of Linear Relationship

A positive slope would indicate that as the amount of catalyst increases, so does the reaction time. Conversely, a negative slope – as seen in the exercise's data set – suggests that higher amounts of catalyst decrease the reaction time. Understanding this principle allows students to extrapolate data and make informed decisions or predictions in their analyses.
The Role of Statistical Analysis
Statistical analysis is the cornerstone of interpreting data and making informed conclusions. It involves collecting, organizing, analyzing, interpreting, and presenting data. One key aspect of statistical analysis is the computation and interpretation of the correlation coefficient, denoted as 'r'. This value provides insight into the strength and direction of a linear relationship between two variables.

In educational settings, teaching students to compute 'r' equips them with the ability to quantify relationships within data. A correlation coefficient close to 1 or -1 signifies a strong linear relationship, whereas a value near 0 suggests a weak or no linear relationship.

Applying Statistical Analysis

In our textbook example, calculating 'r' allows students to gauge the strength of the relationship between the amount of catalyst and reaction time. It's a practical application of theoretical statistical concepts, bridging the gap between learning and real-world data interpretation. Moreover, properly applying statistical analysis not only aids in academic pursuits but also enhances problem-solving and critical thinking skills essential in varied professional fields.

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Most popular questions from this chapter

The paper "Developmental and Individual Differences in Pure Numerical Estimation" (Developmental Psychology [2006]: \(189-201)\) describes a study of how young children develop the ability to estimate lengths. Children were shown a piece of paper with two lines. One line was a short line labeled as having length zip. The second line was a much longer line labeled as having length 1000 zips. The child was then asked to draw a line that had a length of a specified number of zips, such as 438 zips. The data in the accompanying table gives the length requested and the average of the actual lengths of the lines drawn by 30 second graders. \begin{tabular}{cc} Requested Length & Second Grade Average Length Drawn \\ \hline 3 & \(37.15\) \\ 7 & \(92.88\) \\ 19 & \(207.43\) \\ 52 & \(272.45\) \\ 103 & \(458.20\) \\ 158 & \(442.72\) \\ 240 & \(371.52\) \\ 297 & \(467.49\) \\ 346 & \(487.62\) \\ 391 & \(530.96\) \\ 438 & \(482.97\) \\ 475 & \(544.89\) \\ 502 & \(515.48\) \\ 586 & \(595.98\) \\ 613 & \(575.85\) \\ 690 & \(605.26\) \\ 721 & \(637.77\) \\ 760 & \(674.92\) \\ 835 & \(701.24\) \\ 874 & \(662.54\) \\ 907 & \(758.51\) \\ 962 & \(749.23\) \\ \hline \end{tabular} a. Construct a scatterplot of \(y=\) second grade average length drawn versus \(x=\) requested length. b. Based on the scatterplot in Part (a), would you suggest using a line, a quadratic curve, or a cubic curve to describe the relationship between \(x\) and \(y\) ? Explain choice c. Using a statistical software package or a graphing calculator, fit a cubic curve to this data and use it to predict average length drawn for a requested length of 500 zips.

The authors of the paper "Flat-footedness is Not a Disadvantage for Athletic Performance in Children Aged II to 15 Years" (Pediatrics [2009]: e386-e392) studied the relationship between \(y=\) arch height and scores on a number of different motor ability tests for 218 children. They reported the following correlation coefficients: $$ \begin{array}{lc} \text { Motor Ability Test } & \begin{array}{c} \text { Correlation between Test } \\ \text { Score and Arch Height } \end{array} \\ \hline \begin{array}{c} \text { Height of counter } \\ \text { movement jump } \end{array} & -0.02 \\ \text { Hopping: average height } & -0.10 \\ \text { Hopping: average power } & -0.09 \\ \text { Balance, closed eyes, } & 0.04 \\ \text { one leg } & \\ \text { Toe flexion } & 0.05 \\ \hline \end{array} $$ a. Interpret the value of the correlation coefficient between average hopping height and arch height. What does the fact that the correlation coefficient is negative say about the relationship? Do higher arch heights tend to be paired with higher or lower average hopping heights? b. The title of the paper suggests that having a small value for arch height (flat-footedness) is not a disadvantage when it comes to motor skills. Do the given correlation coefficients support this conclusion? Explain.

The accompanying data resulted from an experiment in which weld diameter \(x\) and shear strength \(y\) (in pounds) were determined for five different spot welds on steel. A scatterplot shows a strong linear pattern. With \(\sum(x-\bar{x})^{2}=1000\) and \(\sum(x-\bar{x})(y-\bar{y})=8577\), the least-squares line is \(\hat{y}=-936.22+8.577 x\) \(\begin{array}{cccccc}x & 200.1 & 210.1 & 220.1 & 230.1 & 240.0\end{array}\) \(\begin{array}{llllll}y & 813.7 & 785.3 & 960.4 & 1118.0 & 1076.2\end{array}\) a. Because \(1 \mathrm{lb}=0.4536 \mathrm{~kg}\), strength observations can be re-expressed in kilograms through multiplication by this conversion factor: new \(y=0.4536(\) old \(y)\). What is the equation of the least-squares line when \(y\) is expressed in kilograms? b. More generally, suppose that each \(y\) value in a data set consisting of \(n(x, y)\) pairs is multiplied by a conversion factor \(c\) (which changes the units of measurement for \(y\) ). What effect does this have on the slope \(b\) (i.e., how does the new value of \(b\) compare to the value before conversion), on the intercept \(a\), and on the equation of the least-squares line? Verify your conjectures by using the given formulas for \(b\) and \(a\). (Hint: Replace \(y\) with \(c y\), and see what happensand remember, this conversion will affect \(\bar{y}\).)

Consider the four \((x, y)\) pairs \((0,0),(1,1)\), \((1,-1)\), and \((2,0)\) a. What is the value of the sample correlation coefficient \(r\) ? b. If a fifth observation is made at the value \(x=6\), find a value of \(y\) for which \(r>0.5\). c. If a fifth observation is made at the value \(x=6\), find a value of \(y\) for which \(r<0.5\).

Explain why it can be dangerous to use the leastsquares line to obtain predictions for \(x\) values that are substantially larger or smaller than those contained in the sample.

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