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Ch. 10 - Correlation and Regression
Triola - Elementary Statistics 14th Edition
Triola14th EditionElementary StatisticsISBN: 9780137366446Not the one you use?Change textbook
Chapter 10, Problem 10.5.17

Moore’s Law In 1965, Intel cofounder Gordon Moore initiated what has since become known as Moore’s law: The number of transistors per square inch on integrated circuits will double approximately every 18 months. In the table below, the first row lists different years and the second row lists the number of transistors (in thousands) for different years.
Table showing years from 1971 to 2018 and corresponding transistor counts in thousands, illustrating exponential growth.
Ignoring the listed data and assuming that Moore’s law is correct and transistors per square inch double every 18 months, which mathematical model best describes this law: linear, quadratic, logarithmic, exponential, power? What specific function describes Moore’s law?
Which mathematical model best fits the listed sample data?
Compare the results from parts (a) and (b). Does Moore’s law appear to be working reasonably well?

Verified step by step guidance
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Step 1: Understand Moore's Law states that the number of transistors per square inch doubles approximately every 18 months. This implies exponential growth because the quantity grows by a constant factor (doubling) over equal time intervals.
Step 2: Express Moore's Law mathematically as an exponential function. Let \(N(t)\) be the number of transistors at time \(t\) (in months) since a starting point \(t=0\). The function can be written as: \[N(t) = N_0 \times 2^{\frac{t}{18}}\] where \(N_0\) is the initial number of transistors at \(t=0\).
Step 3: Analyze the given data by plotting the number of transistors against time (years) or by transforming the data using logarithms to check if the growth is exponential. For example, take the logarithm of the transistor counts and see if it forms a linear pattern over time, which would confirm exponential growth.
Step 4: Compare the actual data to the exponential model. If the data closely follows the curve predicted by \(N(t) = N_0 \times 2^{\frac{t}{18}}\), then Moore's Law is working well. If the data deviates significantly, consider fitting other models such as linear, quadratic, or power functions to see which fits best.
Step 5: Conclude by comparing the model from part (a) (the theoretical exponential model) with the best fit model from part (b) (based on actual data). Discuss whether the exponential model accurately describes the transistor growth over the years and if Moore's Law holds true in practice.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Exponential Growth

Exponential growth describes a process where a quantity increases by a consistent percentage over equal time intervals. In Moore’s law, the number of transistors doubles approximately every 18 months, indicating exponential growth. This means the transistor count grows multiplicatively, not additively, over time.

Mathematical Modeling

Mathematical modeling involves selecting a function type (linear, quadratic, exponential, etc.) that best fits observed data or theoretical assumptions. For Moore’s law, the model should reflect doubling behavior, so an exponential function is appropriate. Comparing models helps verify if the data aligns with the theoretical law.
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Data Analysis and Model Fitting

Data analysis involves examining the given transistor counts over years to see if they follow the predicted exponential trend. Model fitting uses statistical methods to find the best function that describes the data. This step is crucial to assess whether Moore’s law accurately predicts real-world transistor growth.
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Related Practice
Textbook Question

Testing for a Linear Correlation

In Exercises 13–28, construct a scatterplot, and find the value of the linear correlation coefficient r. Also find the P-value or the critical values of r from Table A-6. Use a significance level of α = 0.05. Determine whether there is sufficient evidence to support a claim of a linear correlation between the two variables. (Save your work because the same data sets will be used in Section 10-2 exercises.)

Taxis The table below includes data from New York City taxi rides (from Data Set 32 “Taxis” in Appendix B). The distances are in miles, the times are in minutes, the fares are in dollars, and the tips are in dollars. Is there sufficient evidence to support the claim that there is a linear correlation between the time of the ride and the tip amount? Does it appear that riders base their tips on the time of the ride?


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Textbook Question

Super Bowl and R^2 Let x represent years coded as 1,1,3,... for years starting in 1980, and let y represent the numbers of points scored in each annual Super Bowl beginning in 1980. Using the data from 1980 to the last Super Bowl at the time of this writing, we obtain the following values of R^2 for the different models: linear: 0.008; quadratic: 0.023; logarithmic: 0.0004; exponential: 0.027; power: 0.007. Based on these results, which model is best? Is the best model a good model? What do the results suggest about predicting the number of points scored in a future Super Bowl game?

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Textbook Question

Finding the Best Model

In Exercises 5–16, construct a scatterplot and identify the mathematical model that best fits the given data. Assume that the model is to be used only for the scope of the given data, and consider only linear, quadratic, logarithmic, exponential, and power models.

CD Yields The table lists the value y (in dollars) of \$1000 deposited in a certificate of deposit at Bank of New York (based on rates currently in effect).

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Textbook Question

Large Data Sets

Exercises 29–32 use the same Appendix B data sets as Exercises 29–32 in Section 10-1. In each case, find the regression equation, letting the first variable be the predictor (x) variable. Find the indicated predicted values following the prediction procedure summarized in Figure 10-5.

Taxis Repeat Exercise 16 using all of the distance/tip data from the 703 taxi rides listed in Data Set 32 “Taxis” from Appendix B.

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Textbook Question

Interpreting the Coefficient of Determination

In Exercises 5–8, use the value of the linear correlation coefficient r to find the coefficient of determination and the percentage of the total variation that can be explained by the linear relationship between the two variables.

Times of Taxi Rides and Tips r = 0.298 (x = time in minutes, y = the amount of tip in dollars)

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Textbook Question

Regression and Predictions

Exercises 13–28 use the same data sets as Exercises 13–28 in Section 10-1.


Find the regression equation, letting the first variable be the predictor (x) variable.

Find the indicated predicted value by following the prediction procedure summarized in Figure 10-5.


Powerball Jackpots and Tickets Sold Listed below are the same data from Table 10-1 in the Chapter Problem, but an additional pair of values has been added from actual Powerball results. (Jackpot amounts are in millions of dollars, ticket sales are in millions.) Find the best predicted number of tickets sold when the jackpot was actually 345 million dollars. How does the result compare to the value of 55 million tickets that were actually sold?


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