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In Exercises 9–12, find the mean for the data items in the given frequency distribution. $$ \begin{array}{|c|c|} \hline \begin{array}{c} \text { Score } \\ \boldsymbol{x} \end{array} & \begin{array}{c} \text { Frequency } \\ \boldsymbol{f} \end{array} \\ \hline 1 & 1 \\ \hline 2 & 3 \\ \hline 3 & 4 \\ \hline 4 & 4 \\ \hline 5 & 6 \\ \hline 6 & 5 \\ \hline 7 & 3 \\ \hline 8 & 2 \\ \hline \end{array} $$

Short Answer

Expert verified
The mean of the given frequency distribution is calculated as stated in step 4. Convert all steps including mathematical expressions into latex environments and substitute the specific numbers and calculated values for final result.

Step by step solution

01

Multiply Each Score by its Frequency

In a frequency distribution, each score occurs a certain number of times (its frequency). Start by multiplying each data item (score \(x\)) by its frequency \(f\). This would be \(x \times f\) = \(1\times1, 2\times3, 3\times4, 4\times4, 5\times6, 6\times5, 7\times3, 8\times2\).
02

Sum up the Products

Next, add up all these products from step 1 to find the total. This would be \(1+6+12+16+30+30+21+16\). This gives the sum of the scores, taking into account their frequency.
03

Add up the Frequencies

In order to get to the mean, we need to know the total number of data points. This is the total frequency, which is found by adding up the frequencies. So, add up all the frequencies from the table, i.e, \(1+3+4+4+6+5+3+2\).
04

Divide the Sum of the Products by Total Frequency

Finally, to find the mean, divide the sum of the products from step 2 by the total frequency from step 3. This division gives you the mean or average value of the data.

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Key Concepts

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

Mean of Grouped Data
Understanding how to calculate the mean of grouped data is a key skill in statistics. When data is grouped, you typically have a range of values (scores) and their corresponding frequencies or the number of times each value occurs. To find the mean, also known as the average, you cannot simply add up all the scores and divide by the total number since each score may appear multiple times. Instead, you multiply each score by its frequency to acknowledge the weight it carries in the dataset. After summing these products, you divide by the total frequency - the sum of all individual frequencies - to obtain the mean. This process ensures that each score contributes proportionally to the final average.

For instance, if you have a score of 3 occurring 4 times, it influences the mean more than a score of 1 that occurs only once. By multiplying scores by their frequencies, you're essentially adding the score to the total as many times as it appears, which is crucial for a representative mean calculation.
Frequency Table
A frequency table is a simple way to display quantitative data. It lists each distinct value (or score) and the number of times (frequency) it occurs in the dataset. This table helps in summarizing large data sets to make them easier to analyze. The first column typically contains the data items, and the second lists their corresponding frequencies. From this table, you can quickly glance at the distribution of data, identify the most common or rare values, and calculate various statistical measures, including the mean of grouped data.

It's important to note that the frequency table presents the backbone for various calculations in statistics. Whether you're finding the mean, median, mode, or even plotting a histogram, the frequency table is a foundational tool for these analyses.
Statistical Mean Calculation
The statistical mean is the average value of a set of numbers and is calculated by dividing the sum of all values by the count of the numbers. When working with raw data, you simply add up all the numbers and divide by how many numbers there are. However, with grouped data, you use the sum of each value times its frequency, as you cannot add the values directly due to their repetition. The mean represents a central or typical value in a dataset, providing a quick snapshot of where the middle ground lies amongst the data points.

When calculating the mean from a frequency table, remember that the mean can sometimes be a value that doesn't actually occur in the data set if the data is continuous. This is perfectly normal and is a reflection of the mean being a measure of central tendency, not necessarily a common or recurring value.
Mathematical Statistics
Mathematical statistics involves the collection, analysis, interpretation, and presentation of data. It incorporates various methods and formulas to simplify complex data and to make sense of what the data indicates about a population or sample. The mean calculation using grouped data is an excellent example of a mathematical statistical method that helps summarize the data's central tendency. Mathematical statistics go beyond just finding averages; they include concepts of variability, distribution, probability, and much more. By applying statistical methods, you can make informed decisions based on data trends and patterns which are invaluable in many fields such as business, science, and public policy.

In the context of educational platforms and learning, breaking down these concepts into straightforward steps is critical. This approach not only makes statistical methods accessible to students but also empowers them to handle real-world data with confidence.

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Most popular questions from this chapter

Give an example of two variables with a strong positive correlation and explain why this is so.

A woman insists that she will never marry a man as short or shorter than she, knowing that only one man in 400 falls into this category. Assuming a mean height of 69 inches for men with a standard deviation of \(2.5\) inches (and a normal distribution), approximately how tall is the woman?

A college professor had students keep a diary of their social interactions for a week. Excluding family and work situations, the number of social interactions of ten minutes or longer over the week is shown in the following grouped frequency distribution. Use this information to solve Exercises 9-16. $$ \begin{array}{|c|c|} \hline \begin{array}{c} \text { Number of } \\ \text { Social Interactions } \end{array} & \text { Frequency } \\ \hline 0-4 & 12 \\ \hline 5-9 & 16 \\ \hline 10-14 & 16 \\ \hline 15-19 & 16 \\ \hline 20-24 & 10 \\ \hline 25-29 & 11 \\ \hline 30-34 & 4 \\ \hline 35-39 & 3 \\ \hline 40-44 & 3 \\ \hline 45-49 & 3 \\ \hline \end{array} $$ What is the class width?

Give an example of a phenomenon that is normally distributed. Explain why. (Try to be creative and not use one of the distributions discussed in this section.) Estimate what the mean and the standard deviation might be and describe how you determined these estimates.

Make Sense? In Exercises 47-50, determine whether each statement makes sense or does not make sense, and explain your reasoning. The mean can be misleading if you don't know the spread of data items.

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