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Ch. 2 - Descriptive Statistics
Larson - Elementary Statistics: Picturing the World 8th Edition
Larson8th EditionElementary Statistics: Picturing the WorldISBN: 9780137493470Not the one you use?Change textbook
Chapter 2, Problem 2.5.27c

Studying Refer to the data set in Exercise 23 and the box-and-whisker plot you drew that represents the data set.


c. You randomly select one student from the sample. What is the likelihood that the student studied less than 2 hours per day? Write your answer as a percent.

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Step 1: Review the box-and-whisker plot you created for the data set in Exercise 23. Identify the range of values represented on the plot, including the minimum, first quartile (Q1), median, third quartile (Q3), and maximum.
Step 2: Determine the portion of the data that represents students who studied less than 2 hours per day. This can be done by identifying where the value of 2 hours falls on the box-and-whisker plot relative to the quartiles.
Step 3: Calculate the percentage of the data that falls below 2 hours. If 2 hours is less than Q1, for example, then the percentage of students studying less than 2 hours would correspond to the proportion of the data below Q1 (typically 25%).
Step 4: If the value of 2 hours falls within a specific quartile range, use the distribution of data within that range to estimate the percentage of students studying less than 2 hours. For example, if 2 hours is between Q1 and the median, you would estimate the proportion of data in that segment.
Step 5: Convert the proportion of students studying less than 2 hours into a percentage by multiplying the proportion by 100. Write your final answer as a percentage.

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Key Concepts

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

Box-and-Whisker Plot

A box-and-whisker plot is a graphical representation of a data set that displays its minimum, first quartile, median, third quartile, and maximum. It helps visualize the distribution and identify outliers. Understanding this plot is crucial for interpreting the data set and determining the range of study hours.
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Residuals and Residual Plots

Probability

Probability is a measure of the likelihood that a particular event will occur, expressed as a number between 0 and 1 or as a percentage. In this context, it involves calculating the proportion of students who studied less than 2 hours per day relative to the total number of students in the sample.
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Introduction to Probability

Percentages

A percentage is a way of expressing a number as a fraction of 100, which is useful for comparing proportions. In this question, converting the probability of selecting a student who studied less than 2 hours into a percentage allows for a clearer understanding of the likelihood in a familiar format.
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Related Practice
Textbook Question

Extending Concepts


Golf The distances (in yards) for nine holes of a golf course are listed.

336 393 408 522 147 504 177 375 360


d. Use your results from part (c) to explain how to quickly find the mean and the median of the original data set when the distances are converted to inches.

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Textbook Question

Using and Interpreting Concepts


Using and Interpreting Concepts Finding Quartiles, Interquartile Range, and Outliers In Exercises 11 and 12,

(c) identify any outliers.


56 63 51 60 57 60 60 54 63 59 80 63 60 62 65

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Textbook Question

Use the data set and the indicated number of classes to construct

(c) a frequency polygon,


Hospitals

Number of classes: 8

Data set: Number of hospitals in each of the 50 U.S. states and 5 inhabited territories (Source: American Hospital Directory) 10 90 51 1 77 341 56 34 8 214 111 3 14 40 18 142 102 55 75 108 72 53 19 105 55 83 1 69 19 108 10 27 14 78 37 31 186 146 90 37 177 52 11 67 25 100 361 35 91 2 7 61 78 33 14

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Textbook Question

What Would You Do? You work at a bank and are asked to recommend the amount of cash to put in an ATM each day. You do not want to put in too much (which would cause security concerns) or too little (which may create customer irritation). The daily withdrawals (in hundreds of dollars) for 30 days are listed. 72 84 61 76 104 76 86 92 80 88 98 76 97 82 84 67 70 81 82 89 74 73 86 81 85 78 82 80 91 83

If you are willing to run out of cash on 10% of the days, how much cash should you put in the ATM each day? Explain.

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Textbook Question

Pearson’s Index of Skewness The English statistician Karl Pearson (1857–1936) introduced a formula for the skewness of a distribution.

P = 3 (x̄ - median) / s

Most distributions have an index of skewness between -3 and 3. When P > 0, the data are skewed right. When P < 0, the data are skewed left. When P = 0, the data are symmetric. Calculate the coefficient of skewness for each distribution. Describe the shape of each.


c. x̄ = 9.2, s = 1.8, median = 9.2

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Textbook Question

Use the frequency histogram

describe any patterns with the data..

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