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Basic Computation: Weighted Average Find the weighted average of a data set where 10 has a weight of \(2 ; 20\) has a weight of \(3 ; 30\) has a weight of 5

Short Answer

Expert verified
The weighted average is 23.

Step by step solution

01

Understand the Concept of Weighted Average

A weighted average is similar to a regular average, but it takes into account the importance, or weight, of each value. The formula for the weighted average is: \( \frac{\sum (x_i \cdot w_i)}{\sum w_i} \), where \(x_i\) are the data values and \(w_i\) are the corresponding weights.
02

Multiply Each Value by Its Weight

Calculate the product of each data value and its corresponding weight: \(10 \times 2 = 20\), \(20 \times 3 = 60\), and \(30 \times 5 = 150\).
03

Sum the Products

Add all the products from Step 2 to find the total: \(20 + 60 + 150 = 230\).
04

Sum the Weights

Add all the weights given: \(2 + 3 + 5 = 10\).
05

Compute the Weighted Average

Divide the sum of the products by the sum of the weights: \( \frac{230}{10} = 23\). This is the weighted average.

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Key Concepts

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

Statistical Concepts
The concept of weighted average is a fundamental statistical tool used to find an average that reflects varying degrees of importance among quantities. Unlike an ordinary average where each number contributes equally, a weighted average assigns different weights to each value. This means some numbers count more towards the final average based on their assigned weight. This statistic is particularly useful in fields ranging from finance to sociology, where not all data points carry the same significance. For instance, in a student's grade point average, courses that are worth more credits have a higher impact than those worth fewer credits. The formula for the weighted average is:\[ \text{Weighted Average} = \frac{\sum (x_i \cdot w_i)}{\sum w_i} \]Where:
  • \( x_i \) represents each value in the dataset.
  • \( w_i \) is the respective weight of each value.
Understanding this concept is essential for data analysis and making informed decisions based on various values with different levels of importance.
Data Analysis
Data analysis involves interpreting complex data to draw meaningful insights, and using a weighted average is a common technique in this process. When analyzing data, one significant aspect is understanding variance within the dataset—how different parts of the data influence the outcomes. In our exercise, weighing individual numbers helps clarify their relative importance and gives a clearer overall picture compared to using a simple mean that assumes equal weight. ### Applying Data Analysis with Weights In practical scenarios:
  • Companies use weighted averages to calculate average production costs where different materials contribute unequally to the total.
  • Weighted averages can adjust scores in assessments to give more significance to important tests or assignments.
By applying the weighted average, we can highlight crucial data points and ensure analysis reflects real-world scenarios more accurately, making decision-making more precise.
Mathematical Computation
Mathematical computation ensures the accurate and reliable application of formulas like the weighted average. The formula \( \frac{\sum (x_i \cdot w_i)}{\sum w_i} \) might look complex initially, but breaking it down simplifies calculation. ### Step-by-Step Computational Process1. **Multiply Each Value by Its Weight:** - For the given values, execute: - \(10 \times 2 = 20\) - \(20 \times 3 = 60\) - \(30 \times 5 = 150\) 2. **Sum the Products** - Add the results of the products: \(20 + 60 + 150 = 230\) 3. **Sum the Weights** - Calculate the total of all weights: \(2 + 3 + 5 = 10\) 4. **Calculate the Weighted Average** - Divide the total product sum by the total weight sum: \( \frac{230}{10} = 23 \) Performing these computations accurately is vital for ensuring the calculated weighted average reflects the intended weighting of each value, crucial for precise statistical analysis and decision-making based on data.

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Most popular questions from this chapter

What are the big corporations doing with their wealth? One way to answer this question is to examine profits as percentage of assets. A random sample of 50 Fortune 500 companies gave the following information (Source: Based on information from Fortune 500, Vol. 135, No. 8). $$\begin{array}{l|ccccc} \hline \begin{array}{l} \text { Profit as percentage } \\ \text { of assets } \end{array} & 8.6-12.5 & 12.6-16.5 & 16.6-20.5 & 20.6-24.5 & 24.6-28.5 \\ \hline \begin{array}{l} \text { Number of } \\ \text { companies } \end{array} & 15 & 20 & 5 & 7 & 3 \\ \hline \end{array}$$ Estimate the sample mean, sample variance, and sample standard deviation for profit as percentage of assets.

Consider the data set \(2 \quad 3 \quad 4 \quad 5 \quad 6\) (a) Find the range. (b) Use the defining formula to compute the sample standard deviation \(s\) (c) Use the defining formula to compute the population standard deviation \(\sigma .\)

In some reports, the mean and coefficient of variation are given. For instance, in Statistical Abstract of the United States, 116 th edition, one report gives the average number of physician visits by males per year. The average reported is \(2.2,\) and the reported coefficient of variation is \(1.5 \% .\) Use this information to determine the standard deviation of the annual number of visits to physicians made by males.

Given the sample data \(\begin{array}{cccccccc}x: & 23 & 17 & 15 & 30 & 25\end{array}\) (a) Find the range. (b) Verify that \(\Sigma x=110\) and \(\Sigma x^{2}=2568\) (c) Use the results of part (b) and appropriate computation formulas to compute the sample variance \(s^{2}\) and sample standard deviation \(s\) (d) Use the defining formulas to compute the sample variance \(s^{2}\) and sample standard deviation \(s\) (e) Suppose the given data comprise the entire population of all \(x\) values. Compute the population variance \(\sigma^{2}\) and population standard deviation \(\sigma .\)

In this problem, we explore the effect on the standard deviation of multiplying each data value in a data set by the same constant. Consider the data set 5,9,10,11,15 (a) Use the defining formula, the computation formula, or a calculator to compute \(s\) (b) Multiply each data value by 5 to obtain the new data set 25,45,50,55 75. Compute \(s\) (c) Compare the results of parts (a) and (b). In general, how does the standard deviation change if each data value is multiplied by a constant \(c ?\) (d) You recorded the weekly distances you bicycled in miles and computed the standard deviation to be \(s=3.1\) miles. Your friend wants to know the standard deviation in kilometers. Do you need to redo all the calculations? Given 1 mile \(\approx 1.6\) kilometers, what is the standard deviation in kilometers?

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