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Describe each of the following correlation coefficients using the terms strong, moderate, or weak and positive or negative. a. \(r = 0.21 \qquad\) b. \(r = – 0.87\) c. \(r = 0.55 \qquad\) d. \(r = – 0.099\) e. \(r = 0.99 \qquad\) f. \(r = – 0.49\)

Short Answer

Expert verified
a. weak positive, b. strong negative, c. moderate to strong positive, d. weak negative, e. very strong positive, f. moderate negative

Step by step solution

01

Determine Correlation Strength and Direction for \(r = 0.21\)

The value of the correlation coefficient is 0.21, which falls in the range of 0.1 to 0.5. Hence it indicates weak positive correlation.
02

Determine Correlation Strength and Direction for \(r = -0.87\)

The value of the correlation coefficient is -0.87, which falls in the range of -0.9 to -0.5. Hence it indicates a strong negative correlation.
03

Determine Correlation Strength and Direction for \(r = 0.55\)

The value of the correlation coefficient is 0.55, which falls in the range of 0.5 to 0.9. Hence it indicates moderate to strong positive correlation.
04

Determine Correlation Strength and Direction for \(r = -0.099\)

The value of the correlation coefficient is -0.099, which falls in the range of -0.1 to -0.5. Hence it indicates weak negative correlation.
05

Determine Correlation Strength and Direction for \(r = 0.99\)

The value of the correlation coefficient is 0.99, which is close to 1. Hence it indicates a very strong positive correlation.
06

Determine Correlation Strength and Direction for \(r = -0.49\)

The value of the correlation coefficient is -0.49, which falls in the range of -0.5 to -0.1. Hence it indicates a moderate negative correlation.

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Key Concepts

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

Correlation Analysis
Correlation analysis is a method used in statistics to measure the strength and direction of a linear relationship between two variables. It gives us a correlation coefficient, usually denoted as \( r \), which can range from \( -1 \) to \( 1 \).

This coefficient tells us two things about the relationship:
  • The direction: Whether the relationship is positive or negative.
  • The strength: How strong or weak the relationship is.

An \( r \) value closer to \( 1 \) or \( -1 \) indicates a stronger relationship, while a value closer to \( 0 \) suggests a weaker relationship. Understanding these nuances can help you analyze data more effectively.
Positive Correlation
Positive correlation occurs when two variables move in the same direction. This means if one variable increases, the other tends to increase as well, and vice versa.

The correlation coefficient \( r \) will be greater than \( 0 \). The closer \( r \) is to \( 1 \), the stronger the positive relationship.
  • Example: \( r = 0.21 \) is a weak positive correlation.
  • Example: \( r = 0.99 \) indicates a very strong positive correlation.

Understanding positive correlation can be useful in fields like finance, psychology, and research where predicting variables in tandem can offer insights.
Negative Correlation
Negative correlation happens when two variables move in opposite directions. If one variable increases, the other decreases.

A negative correlation coefficient \( r \) will be less than \( 0 \). The closer \( r \) is to \( -1 \), the stronger the negative relationship.
  • Example: \( r = -0.87 \) indicates a strong negative correlation.
  • Example: \( r = -0.099 \) shows a weak negative correlation.

Negative correlations are significant in understanding processes where factors inversely affect one another, like supply and demand in economics.
Statistical Strength
Statistical strength refers to how strong or weak the relationship is between two variables. It helps determine the confidence with which we can interpret the relationship.

Here's how it works:
  • Strong correlation: \( |r| \) closer to \( 1 \) or \( -1 \). Reliable indication of linear relationship.
  • Moderate correlation: \( |r| \) in the range of \( 0.5 \) to \( 0.7 \). Shows a reasonable degree of association.
  • Weak correlation: \( |r| \) closer to \( 0 \). Indicates a weaker association between variables.

Recognizing statistical strength is crucial for interpreting data accurately, guiding decision-making, and predicting outcomes reliably.

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Most popular questions from this chapter

Wind Up Corporation manufactures widgets. The monthly expense equation is \(E=3.20 q+56,000\) . They plan to sell the widgets to retailers at a wholesale price of \(\$ 6.00\) each. How many widgets must be sold to reach the break even point?

An electronics store is selling car chargers for cell phones. The expense function is \(E=-300 p+13,000\) and the revenue function is \(R=-32 p^{2}+1,200 p .\) a. At what price would the maximum revenue be reached? b. What would that maximum revenue be? Round to the nearest cent. c. Graph the expense and revenue functions. Circle the breakeven points. d. Determine the prices at the breakeven points. Round to the nearest cent. e. Determine the revenue and expense amounts for each of the breakeven points. Round to the nearest cent.

Variable costs of producing widgets account for the cost of gas required to deliver the widgets to retailers. A widget producer finds the average cost of gas per widget. The expense equation was recently adjusted from \(E=4.55 q+69,000\) to \(E=4.98 q+69,000\) in response to the increase in gas prices. a. Find the increase in the average cost per widget. b. If the widgets are sold to retailers for \(\$ 8.00\) each, find the break even point prior to the adjustment in the expense function. c. After the gas increase, the company raised its wholesale cost from \(\$ 8\) to \(\$ 8.50\) . Find the breaker point after the adjustment in the expense function. Round to the nearest integer.

A supplier of school kits has determined that the combined fixed and variable expenses to market and sell G kits is W. a. What expression models the price of a school kit at the breakeven point? b. Suppose a new marketing manager joined the company and determined that the combined fixed and variable expenses would only be 80% of the cost if the supplier sold twice as many kits. Write an expression for the price of a kit at the breakeven point using the new marketing manager’s business model.

Use the following situation to answer Exercises 4–20. A company produces a security device known as Toejack. Toejack is a computer chip that parents attach between the toes of a child, so parents can track the child’s location at any time using an online system. The company has entered into an agreement with an Internet service provider, so the price of the chip will be low. Set up a demand function—a schedule of how many Toejacks would be demanded by the public at different prices. The horizontal axis represents price, and the vertical axis represents quantity. Does the demand function have a positive or negative slope? Explain.

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