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Ch. 2 - Descriptive Statistics
Larson - Elementary Statistics: Picturing the World 8th Edition
Larson8th EditionElementary Statistics: Picturing the WorldISBN: 9780137493470Non è quello che usi tu?Cambia libro di testo
Capitolo 2, Problema 2.T.3

Use frequency distribution formulas to estimate the sample mean and the sample standard deviation of the data set in Exercise 2.

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Step 1: Organize the data into a frequency distribution table. This table should include columns for class intervals, frequencies (f), midpoints of the class intervals (x), and any other necessary values for calculations.
Step 2: Calculate the midpoint (x) for each class interval. The midpoint is the average of the lower and upper boundaries of the class interval, calculated as \( x = \frac{{\text{lower boundary} + \text{upper boundary}}}{2} \).
Step 3: Compute the weighted sum of the midpoints by multiplying each midpoint (x) by its corresponding frequency (f). Sum these products to find \( \sum f \cdot x \).
Step 4: Estimate the sample mean using the formula \( \text{Sample Mean} = \frac{{\sum f \cdot x}}{\sum f} \), where \( \sum f \) is the total frequency.
Step 5: Estimate the sample standard deviation using the formula \( \text{Sample Standard Deviation} = \sqrt{\frac{{\sum f \cdot (x - \text{Sample Mean})^2}}{\sum f}} \). For this, calculate \( (x - \text{Sample Mean})^2 \) for each class interval, multiply by the frequency (f), sum these values, and divide by \( \sum f \). Finally, take the square root of the result.

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Frequency Distribution

A frequency distribution is a summary of how often each value occurs in a dataset. It organizes data into categories or intervals, allowing for easier analysis of patterns and trends. Understanding frequency distributions is essential for calculating measures like the sample mean and standard deviation, as it provides a clear view of data distribution.
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06:38
Intro to Frequency Distributions

Sample Mean

The sample mean is the average of a set of values, calculated by summing all the data points and dividing by the number of observations. It serves as a measure of central tendency, providing insight into the overall level of the data. In the context of frequency distributions, the sample mean can be estimated by weighting the midpoints of intervals by their frequencies.
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Sampling Distribution of Sample Proportion

Sample Standard Deviation

The sample standard deviation quantifies the amount of variation or dispersion in a set of values. It is calculated by taking the square root of the variance, which measures how far each data point is from the sample mean. In frequency distributions, the standard deviation can be estimated using the frequencies and midpoints of the intervals, reflecting the spread of the data.
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08:45
Calculating Standard Deviation
Pratica correlata
Domanda del libro di testo

The overall averages of 12 students in a statistics class prior to taking the final exam are listed.

67 72 88 73 99 85 81 87 63 94 68 87


d. Display the data in a stem-and-leaf plot. Use one line per stem.

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Domanda del libro di testo

"According to data from the city of Toronto, Ontario, Canada, there were nearly 112,000 parking infractions in the city for December 2020, with fines totaling over 5,500,000 Canadian dollars. The fines (in Canadian dollars) for a random sample of 105 parking infractions in Toronto, Ontario, Canada, for December 2020 are listed below. (Source: City of Toronto)


In Exercises 1–5, use technology. If possible, print your results.


Draw a histogram for the data. Does the distribution appear to be bell-shaped?"

54
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Domanda del libro di testo

The overall averages of 12 students in a statistics class prior to taking the final exam are listed.

67 72 88 73 99 85 81 87 63 94 68 87


a. Find the mean, median, and mode of the data set. Which best represents the center of the data?

95
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Domanda del libro di testo

The number of minutes it took 12 students in a statistics class to complete the final exam are listed. Use a scatter plot to display this data set and the data set in Exercise 1. The data sets are in the same order. Describe any patterns.

61 85 67 48 54 61 59 80 67 55 88 84

72
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Domanda del libro di testo

According to data from the city of Toronto, Ontario, Canada, there were nearly 112,000 parking infractions in the city for December 2020, with fines totaling over 5,500,000 Canadian dollars. The fines (in Canadian dollars) for a random sample of 105 parking infractions in Toronto, Ontario, Canada, for December 2020 are listed below. (Source: City of Toronto)


In Exercises 1–5, use technology. If possible, print your results.


Find the sample mean of the data.

91
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Domanda del libro di testo

The data set represents the number of movies that a sample of 20 people watched in a year.

121 148 94 142 170 88 221 106 18 67

149 28 60 101 134 168 92 154 53 66


c. Display the data using a relative frequency histogram.

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