/*! 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 18 The following table shows data o... [FREE SOLUTION] | 91Ó°ÊÓ

91Ó°ÊÓ

The following table shows data on gender \((\) coded as \(1=\) female \(, 2=\) male \()\) and preferred type of chocolate \((\) coded as \(1=\) white, \(2=\) milk, \(3=\) dark \()\) for a sample of 10 students. The students' teacher enters the data into software and reports a correlation of 0.640 between gender and type of preferred chocolate. He concludes that there is a moderately strong positive correlation between someone's gender and chocolate preference. What's wrong with this analysis?

Short Answer

Expert verified
The data types are categorical, so correlation is unsuitable and invalid.

Step by step solution

01

Understand the Data

The data presented consists of categories that are coded numerically: gender is labeled with 1 for female and 2 for male, while chocolate preference is coded as 1 for white, 2 for milk, and 3 for dark.
02

Recognize Data Types

Both gender and chocolate preference are categorical variables, even though they are represented with numerical codes. These numbers do not indicate any inherent mathematical order or quantitative relationship.
03

Identify the Inappropriate Use of Correlation

Correlation is a statistical measure used to describe the linear relationship between two continuous numerical variables. In this case, since both variables are categorical, the calculation of correlation lacks proper validity.
04

Conclude the Issue with the Analysis

The reported correlation is 0.640, and the interpretation as a moderately strong positive correlation between gender and chocolate preference is incorrect because correlation is not suitable for categorical data. Appropriate methods for analyzing such data include contingency tables or chi-squared tests.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!

Key Concepts

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

Categorical Variables
When we deal with categorical variables, we refer to data that can be grouped into specific categories or groups. In our example, gender and chocolate preference are both categorical variables, as they represent non-quantitative groups. For gender, values such as "female" and "male" are categories, just like chocolate preference categories are "white," "milk," and "dark."

It's important to note that while categorical variables may be coded with numbers, these numbers do not signify any math-related value or order. They are merely labels assigned to different categories. Therefore, treating these labels as numerical values, as in calculating correlation, can be misleading. Understanding this distinction is crucial to ensuring the proper statistical analyses are performed. The focus should be on categories themselves, not the numeric representation.
Chi-Squared Test
The chi-squared test is a statistical method commonly used to analyze data in the form of categories. It helps in determining whether there's a significant association between two categorical variables. Unlike correlation, which measures linear relationships between numerical data, the chi-squared test assesses the expected frequency of data points within the different categories.

In the scenario provided, since gender and chocolate preference are categorical, a chi-squared test could be more appropriate to see if there is a relationship between these variables. This involves creating a contingency table, which shows the frequency distribution between the categories. The chi-squared test then examines whether the observed frequencies significantly deviate from what we would expect if there were no association between the categories, providing a more fitting analysis for categorical data.
Data Misinterpretation
Data misinterpretation can easily occur when inappropriate statistical methods are applied. One common mistake is using correlation to examine relationships between categorical variables, as was done in our example. This results in misinterpretation because the method requires the variables to be continuous and numerical.

Misinterpretation through inappropriate tools may lead to incorrect conclusions, such as claiming a significant correlation where it doesn't exist. Such errors emphasize the importance of choosing the right statistical methods based on the data types at hand. Always ensure that the analysis technique matches the variable types to avoid false results.

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Explain what's wrong with the way regression is used in each of the following examples: a. Winning times in the Boston marathon (at www. bostonmarathon.org) have followed a straight-line decreasing trend from 160 minutes in 1927 (when the race was first run at the Olympic distance of about 26 miles) to 128 minutes in 2014. After fitting a regression line to the winning times, you use the equation to predict that the winning time in the year 2300 will be about 13 minutes. b. Using data for several cities on \(x=\%\) of residents with a college education and \(y=\) median price of home, you get a strong positive correlation. You conclude that having a college education causes you to be more likely to buy an expensive house. c. A regression between \(x=\) number of years of education and \(y=\) annual income for 100 people shows a modest positive trend, except for one person who dropped out after 10 th grade but is now a multimillionaire. It's wrong to ignore any of the data, so we should report all results including this point. For this data, the correlation \(r=-0.28\)

In an introductory statistics course, \(x=\) midterm exam score and \(y=\) final exam score. Both have mean \(=80\) and standard deviation \(=10\). The correlation between the exam scores is 0.70 . a. Find the regression equation. b. Find the predicted final exam score for a student with midterm exam score \(=80\) and another with midterm exam score \(=90\).

In a survey conducted in March 2013 by the National Consortium for the Study of Terrorism and Responses to Terrorism, 1515 adults were asked about the effectiveness of the government in preventing terrorism and whether they believe that it could eventually prevent all major terrorist attacks. \(37.06 \%\) of the 510 adults who consider the government to be very effective believed that it can eventually prevent all major attacks, while this proportion was \(28.36 \%\) among those who consider the government somewhat, not too, or not at all effective in preventing terrorism. The other people surveyed considered that terrorists will always find a way. a. Identify the response variable, the explanatory variable and their categories. b. Construct a contingency table that shows the counts for the different combinations of categories. c. Use a contingency table to display the percentages for the categories of the response variables, separately for each category of the explanatory variable. d. Are the percentages reported in part c conditional? Explain. e. Sketch a graph that compares the responses for each category of the explanatory variable. fo Compute the difference and the ratio of proportions. Interpret. g. Give an example of how the results would show that there is no evidence of association between these variables.

According to data selected from GSS in \(2014,\) the correlation between \(y=\) email hours per week and \(x=\) ideal number of children is -0.0008 a. Would you call this association strong or weak? Explain. b. The correlation between email hours per week and Internet hours per week is \(0.33 .\) For this sample, which explanatory variable, ideal number of children or Internet hours per week, seems to have a stronger association with \(y ?\) Explain.

The weight (in carats) and the price (in millions of dollars) of the 9 most expensive diamonds in the world was collected from www.elitetraveler.com. Let the explanatory variable \(x=\) weight and the response variable \(y=\) price. The regression equation is \(\hat{y}=109.618+0.043 x\). a. Princie is a diamond whose weight is 34.65 carats. Use the regression equation to predict its price. b. The selling price of Princie is \(\$ 39.3\) million. Calculate the residual associated with the diamond and comment on its value in the context of the problem. c. The correlation coefficient is \(0.053 .\) Does it mean that a diamond's weight is a reliable predictor of its price?

See all solutions

Recommended explanations on Math Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.