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Multiple Choice: Select the best answer for Exercises 45 to 48. Suppose that the relationship between a response variable y and an explanatory variable x is modeled by\(y=2.7(0.316)^{x}\). Which of the following scatterplots would approximately follow a straight line? (a) A plot of y against x (b) A plot of y against log x (c) A plot of log y against x (d) A plot of log y against log x (e) None of (a) through (d)

Short Answer

Expert verified
The correct answer is (c).

Step by step solution

01

Understand the Function Form

The function given is \( y = 2.7 \times 0.316^x \). This is an exponential decay function, where the base of the exponential term (0.316) is less than 1, causing \( y \) to decrease as \( x \) increases.
02

Determine Linearization Strategy

To find if a certain transformation would yield a straight line, we need to transform the equation of \( y \) so that it becomes linear. For an exponential equation like \( y = ab^x \), taking the logarithm of both sides turns it into a linear form: \( \log y = \log (ab^x) = \log a + x\log b \).
03

Apply Logarithm to the Given Function

Applying the logarithm to both sides of the equation \( y = 2.7 \times 0.316^x \) gives us: \( \log y = \log 2.7 + x \log 0.316 \). This is now in the form of a linear equation, \( \log y = \text{constant} + x \times \text{(constant)} \).
04

Identify the Linear Plot

From the transformed equation \( \log y = \log 2.7 + x \log 0.316 \), we observe that by plotting \( \log y \) against \( x \), we obtain a straight line. Thus, choice (c) "A plot of log y against x" will approximately form a straight line.

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Key Concepts

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

Response Variable
In common terms, a response variable is what you're trying to measure or predict in an experiment or study. It is sometimes called the dependent variable because its value depends on the explanatory variable.
  • In the given exercise, the response variable is represented by \( y \) in the function \( y = 2.7 \times 0.316^x \).
  • This variable is influenced by changes in \( x \), making it perfect for observing how it reacts or changes due to different conditions.
Understanding the role of the response variable in the context of an exponential decay function is essential. It helps us identify what outcome or behavior we are assessing. In the scenario given, \( y \) decreases as \( x \) increases, clearly indicating an exponential decay. This means as you increase \( x \), the value of \( y \) exponentially decreases.
Explanatory Variable
The explanatory variable is what you control or manipulate to see how it affects the response variable. It is often referred to as the independent variable.
  • Here, the explanatory variable is \( x \). It is used to test the effect on the response variable \( y \).
  • As you alter \( x \), you assess how \( y \) changes accordingly. This makes \( x \) a critical component in understanding relationships in the data.
In the given exercise, tracking the changes in \( x \) allows us to interpret the behavior of our function. Recognizing \( x \) as the explanatory variable lets us explore the decay pattern in \( y \) based on exponential relationships. By understanding this, we can make predictions and analyze trends in real-world scenarios where such relationships matter.
Linearization Strategy
Linearizing a function simplifies its analysis by transforming it into a straight line equation. This process makes it easier to interpret and compare results.
  • For an exponential equation like \( y = ab^x \), taking the logarithm of both sides gives us a linear form.
  • In the exercise, applying \( \log \) to the equation \( y = 2.7 \times 0.316^x \) transforms it into \( \log y = \log 2.7 + x \log 0.316 \).
This shows a straightforward linear relationship between \( \log y \) and \( x \). The constant \( \log 2.7 \) is the y-intercept, and \( x \log 0.316 \) is the slope. Such a strategy allows us, for example, to use methods of linear regression to analyze data that originally follows a complex exponential model. It provides a clearer visual representation and easier interpretation of data behavior.
Scatterplots
A scatterplot represents data points on a graph, providing a visual perspective of the relationship between two variables.
  • Each point on a scatterplot corresponds to one data pair from the two variables.
  • It is particularly useful for identifying patterns, trends, or correlations.
In our exercise, different scatterplots plots are considered to identify which one forms a straight line, indicating a linear relationship after transformation. The transformed equation \( \log y = \log 2.7 + x \log 0.316 \) suggests plotting \( \log y \) against \( x \) forms a straight line. Such a scatterplot confirms a linearized relationship proving that logarithmic transformation can make exponential data more interpretable. This is a powerful tool for data analysis as it simplifies complex relationships, making it easier to predict outcomes or identify factors with a significant impact.

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Most popular questions from this chapter

Boyle’s law If you have taken a chemistry class, then you are probably familiar with Boyle’s law: for gas in a confined space kept at a constant temperature, pressure times volume is a constant (in symbols, PV k). Students collected the following data on pressure and volume using a syringe and a pressure probe. (a) Make a reasonably accurate scatterplot of the data by hand using volume as the explanatory variable. Describe what you see. (b) If the true relationship between the pressure and volume of the gas is PV k, we can divide both sides of this equation by V to obtain the theoretical model P k/V, or P k(1/V). Use the graph below to identify the transformation that was used to linearize the curved pattern in part (a). (c) Use the graph below to identify the transformation that was used to linearize the curved pattern in part (a).

Multiple choice: Select the best answer for Exercises 21 to 26. What is the correlation between selling price and appraised value? (a) 0.1126 (c) -0.861 (e) -0.928 (b) 0.861 (d) 0.928

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Exercises 51 and 52 refer to the following setting. About 1100 high school teachers attended a weeklong summer institute for teaching AP classes. After hearing about the survey in Exercise 50, the teachers in the AP Statistics class wondered whether the results of the tattoo survey would be similar for teachers. They designed a survey to find out. The class opted for a sample size of 100 teachers. One of the questions on the survey was Do you have any tattoos on your body? (Circle one) YES NO Tattoos (8.2, 9.2) Of the 98 teachers who responded, 23.5% said that they had one or more tattoos. (a) Construct and interpret a 95% confidence interval for the actual proportion of teachers at the AP institute who would say they had tattoos. (b) Does the interval in part (a) provide convincing evidence that the proportion of teachers at the institute with tattoos is not 0.14 (the value cited in the Harris Poll report)? Justify your answer. (c) Two of the selected teachers refused to respond to the survey. If both of these teachers had responded, could your answer to part (b) have changed? Justify your answer.

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