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For each set of data in Exercises 2.43 to 2.46: (a) Find the mean \(\bar{x}\). (b) Find the median \(m\). (c) Indicate whether there appear to be any outliers. If so, what are they? \(\begin{array}{lllllll}& 41, & 53, & 38, & 32, & 115, & 47, & 50\end{array}\)

Short Answer

Expert verified
The mean is 54, the median is 47, and the outliers are 115.

Step by step solution

01

Calculate the mean

Add all the data points and divide the sum by the count. The data points are 41, 53, 38, 32, 115, 47 and 50. \( \bar{x} = \frac{41 + 53 + 38 + 32 + 115 + 47 + 50}{7} = 54 \)
02

Calculate the median

Arrange the data points in ascending order and find the middle value. If there is an even number of data points, the median would be the mean of the middle two values. The sorted data points are 32, 38, 41, 47, 50, 53, 115. So, the median \(m\) is 47.
03

Identify outliers

Outliers are values that are significantly different from the others. In this case, 115 stands out from the rest of the numbers, so 115 is an outlier.

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Key Concepts

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

Understanding the Mean
The mean, often referred to as the average, is a measure of central tendency that represents the typical value in a set of numbers. To calculate the mean \( \bar{x} \), you sum all the data points and divide by the count. Consider the given dataset: 41, 53, 38, 32, 115, 47, 50. The sum of these numbers is \(41 + 53 + 38 + 32 + 115 + 47 + 50 = 376\), and there are 7 data points. Hence, the mean is \( \bar{x} = 376/7 = 54\).

This value serves as a quick approximation of what a 'typical' data point might be. However, the mean can be highly sensitive to extreme values or outliers, which can skew the mean away from the center of the bulk of the data. This sensitivity is precisely why it is essential to examine other measures of central tendency and to check for outliers, which can provide a more comprehensive understanding of the data's distribution.
Finding the Median
The median is another measure of central tendency that is less affected by outliers and skewed data. To find the median, you need to arrange the data points in ascending order and identify the middle value. For the dataset 41, 53, 38, 32, 115, 47, 50, the ordered list is 32, 38, 41, 47, 50, 53, 115. With seven numbers in this set, the median \( m \) is the fourth number, which is 47.

In situations where the dataset contains an even number of data points, the median is the mean of the two central numbers. The median provides a better central value for skewed distributions because it does not incorporate the magnitude of the outliers, only their position within the ordered dataset.
Identifying Outliers
Outliers are data points that significantly differ from the rest of the dataset. They can arise due to measurement or entry errors, or they can be actual representations of variability in the data. To identify outliers, statisticians often use methods such as the 1.5 \( \times \) interquartile range rule or z-scores, but a simple visual inspection can also suggest their presence.

In the example dataset, the number 115 stands out because it is much higher than the other values, which range from 32 to 53. Thus, 115 can be considered an outlier. Outliers can have a substantial effect on the mean, as seen earlier, and may not be representative of the typical data in the set. It is crucial to investigate the cause of outliers and decide whether they should be included in the analysis, as they can greatly influence the interpretation of the data.

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