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Ch. 3 - Describing, Exploring, and Comparing Data
Triola - Elementary Statistics 14th Edition
Triola14th EditionElementary StatisticsISBN: 9780137366446Not the one you use?Change textbook
Chapter 3, Problem 3.3.25

In Exercises 21–28, use the same list of cell phone radiation levels given for Exercises 17–20. Find the indicated percentile or quartile.


P50


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Step 1: Understand the problem. The task is to find the 50th percentile (P50) of the given data set. The 50th percentile is also known as the median, which is the value that separates the lower half and upper half of the data when arranged in ascending order.
Step 2: Arrange the data in ascending order. From the image, the data is already sorted in ascending order, so no further arrangement is needed.
Step 3: Determine the position of the 50th percentile in the data set. Use the formula for the position: \( P_k = \frac{k}{100} \times (n+1) \), where \( k \) is the percentile (50 in this case) and \( n \) is the total number of data points. Count the total number of data points in the list.
Step 4: Calculate the position using the formula. Substitute \( k = 50 \) and \( n \) (the total number of data points) into the formula. If the position is an integer, the value at that position is the 50th percentile. If the position is not an integer, interpolate between the two closest values.
Step 5: Identify the value corresponding to the calculated position in the sorted data set. This value is the 50th percentile (P50).

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Key Concepts

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

Percentiles

A percentile is a measure used in statistics to indicate the value below which a given percentage of observations fall. For example, the 50th percentile (P50) is the median, meaning that 50% of the data points are below this value. Understanding percentiles helps in interpreting the distribution of data and comparing individual scores to a larger dataset.

Quartiles

Quartiles are specific percentiles that divide a dataset into four equal parts. The first quartile (Q1) represents the 25th percentile, the second quartile (Q2) is the median or 50th percentile, and the third quartile (Q3) is the 75th percentile. Quartiles are useful for understanding the spread and center of a dataset, as they provide insights into the distribution of values.
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Data Distribution

Data distribution refers to the way in which data points are spread or arranged across different values. It can be visualized using graphs like histograms or box plots, which help identify patterns such as skewness, central tendency, and variability. Understanding the distribution of data is crucial for accurately calculating percentiles and quartiles, as these measures depend on the arrangement of the data.
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Related Practice
Textbook Question

In Exercises 21–24, find the mean and median for each of the two samples, then compare the two sets of results.


It’s a Small Wait After All Listed below are the wait times (minutes) at 10 AM for the rides “It’s a Small World” and “Avatar Flight of Passage.” These data are found in Data Set 33 “Disney World Wait Times.” Does a comparison between the means and medians reveal that there is a difference between the two sets of data?

185
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Textbook Question

Critical Thinking. For Exercises 5–20, watch out for these little buggers. Each of these exercises involves some feature that is somewhat tricky. Find the (a) mean, (b) median, (c) mode, (d) midrange, and then answer the given question.


Smart Thermostats Listed below are selling prices (dollars) of smart thermostats tested by Consumer Reports magazine. If you decide to buy one of these smart thermostats, what statistic is most relevant, other than the measures of central tendency?


250 170 225 100 250 250 130 200 150 250 170 200 180 250

139
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Textbook Question

In Exercises 5–20, find the range, variance, and standard deviation for the given sample data. Include appropriate units (such as “minutes”) in your results. (The same data were used in Section 3-1, where we found measures of center. Here we find measures of variation.) Then answer the given questions.


Super Bowl Jersey Numbers Listed below are the jersey numbers of the 11 offensive players on the starting roster of the New England Patriots when they won Super Bowl LIII. What do the results tell us?


12 26 46 15 11 87 77 62 60 69 61

299
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Textbook Question

Critical Thinking. For Exercises 5–20, watch out for these little buggers. Each of these exercises involves some feature that is somewhat tricky. Find the (a) mean, (b) median, (c) mode, (d) midrange, and then answer the given question.


Caffeine in Soft Drinks Listed below are measured amounts of caffeine (mg per 12 oz of drink) obtained in one can from each of 20 brands (7-UP, A&W Root Beer, Cherry Coke, . . . , Tab). Are the statistics representative of the population of all cans of the same 20 brands consumed by Americans?


0 0 34 34 34 45 41 51 55 36 47 41 0 0 53 54 38 0 41 47

142
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Textbook Question

Trimmed Mean Because the mean is very sensitive to extreme values, we say that it is not a resistant measure of center. By deleting some low values and high values, the trimmed mean is more resistant. To find the 10% trimmed mean for a data set, first arrange the data in order, then delete the bottom 10% of the values and delete the top 10% of the values, then calculate the mean of the remaining values. Use the axial loads (pounds) of aluminum cans listed below (from Data Set 41 “Aluminum Cans” in Appendix B) for cans that are 0.0111 in. thick. An axial load is the force at which the top of a can collapses. Identify any outliers, then compare the median, mean, 10% trimmed mean, and 20% trimmed mean.


247 260 268 273 276 279 281 283 284 285 286 288

289 291 293 295 296 299 310 504

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Textbook Question

Large Data Sets from Appendix B. In Exercises 25–28, refer to the indicated data set in Appendix B. Use software or a calculator to find the means and medians.


Body Temperatures Refer to Data Set 5 “Body Temperatures” in Appendix B and use the body temperatures for 12:00 AM on day 2. Do the results support or contradict the common belief that the mean body temperature is 98.6oF?

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