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Specify an important difference between the standard deviation and the mean.

Short Answer

Expert verified
The mean is a measure of central tendency that calculates the average value of a data set, while the standard deviation is a measure of variability that expresses how much the members of a group differ from the mean value of the group.

Step by step solution

01

Define Mean

The mean, often referred to as average, is a measure of central tendency. It's calculated by adding up all the values in a data set, and then dividing by the number of values in that set. For instance, to find the mean of the set 3, 4, 5, you will add the numbers together (3+4+5 = 12) and then divide by the amount of numbers, which in this case is 3. So, the mean of the set is 12/3 = 4.
02

Define Standard Deviation

Standard deviation is a statistical measure that shows the dispersion of a data set from the mean. A smaller standard deviation means that values are closer to the mean, whilst a larger standard deviation indicates that values are spread out over a wider range. To calculate the standard deviation: Firstly, find the mean of the data set. Secondly, subtract the mean from each number in the data set and then square the result. Thirdly, find the mean of those squared differences. Lastly, take the square root of that result.
03

State the Difference

The primary difference between a standard deviation and a mean is that while the standard deviation measures the variability or dispersion for a set of data, the mean provides a measure of central tendency, essentially locating the center of a data set. They are linked, yet entirely different concepts.

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Key Concepts

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

Measure of Central Tendency
Understanding the concept of 'measure of central tendency' is vital in statistics, as it helps to simplify complex data sets by finding a single value that is representative of the entire collection of numbers. Simply put, this measure tells us where the middle of a data set lies. The most common measures include the mean, median, and mode.

Each measure offers a unique way of determining the center of the data. The mean is calculated as the average of all values, the median represents the middle value when all numbers are arranged in order, and the mode is the value that appears most frequently. These central points provide a quick snapshot of the data, which can be especially helpful in making decisions or understanding trends.
Statistical Dispersion
Statistical dispersion indicates the extent to which a data set is spread out or clustered around the central value. It is a critical concept because it tells us about the variability in the data. Without understanding dispersion, the measure of central tendency can be misleading - if all values are the same, the average is highly representative of the data, but if they're widely varied, the average alone isn't enough.

Dispersion is usually detailed with statistics such as range, variance, and standard deviation. Range provides the difference between the highest and lowest values, variance shows the average of the squared differences from the mean, and standard deviation, the most commonly used measure, shows the average distance of each data point from the mean. High dispersion means that the data points are spread out, while low dispersion indicates they are more closely clustered.
Mean Calculation
The mean is the most widely used measure of central tendency and represents the average of a data set. To calculate the mean, follow these simple steps:
  • Sum up all the values in the data set.
  • Count the total number of values.
  • Divide the sum by the total number of values.

This calculation gives you the arithmetic mean, which can be easily influenced by extremely high or low values, known as outliers. However, it's a straightforward and intuitive way to find a 'typical' value within the data.
Standard Deviation Calculation
Standard deviation is a more intricate concept, representing the amount of variation or dispersion in a set of values. To calculate it, follow these steps:
  • Compute the mean of the data set.
  • Subtract the mean from each individual data point and square the result (this is the squared deviation).
  • Add together all these squared deviations.
  • Divide this sum by the number of data points (for a population) or by one less than the number of data points (for a sample, which is a correction for bias).
  • Finally, take the square root of the result to return to the original units of measurement, giving you the standard deviation.

This gives a clear indication of how spread out the values are around the mean. A larger standard deviation suggests that data points are more spread out, while a smaller standard deviation means they are closer to the mean, making the mean a more accurate reflection of the data.

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Most popular questions from this chapter

Add 10 to only the smallest score in Question 4.3(1,3,4,4) to produce another new distribution (11,3,4,4) . Would you expect the value of \(s\) to be the same for both the original and new distributions? Explain your answer, and then calculate s for the new distribution.

Using the computation formula for the sum of squares, calculate the population standard deviation for the scores in (a) and the sample standard deviation for the scores in (b). (a) 1,3,7,2,0,4,7,3 (b) 10,8,5,0,1,1,7,9,2

(a) While in office, a former governor of California proposed that all state employees receive the same pay raise of \(\$ 70\) per month. What effect, if any, would this raise have had on the mean and the standard deviation for the distribution of monthly wages in existence before the proposed raise? Hint: Imagine the effect of adding \(\$ 70\) to the monthly wages of each state employee on the mean and on the standard deviation (or on a more easily visualized measure of variability, such as the range).

Assume that the distribution of IQ scores for all college students has a mean of \(120,\) with a standard deviation of \(15 .\) These two bits of information imply which of the following? (a) All students have an IQ of either 105 or 135 because everybody in the distribution is either one standard deviation above or below the mean. True or false? (b) All students score between 105 and 135 because everybody is within one standard deviation on either side of the mean. True or false? (c) On the average, students deviate approximately 15 points on either side of the mean. True or false? (d) Some students deviate more than one standard deviation above or below the mean. True or false? (e) All students deviate more than one standard deviation above or below the mean. True or false? (f) Scott's IQ score of 150 deviates two standard deviations above the mean. True or false?

Indicate whether each of the following statements about degrees of freedom is true or false. (a) Degrees of freedom refer to the number of values free to vary in the population. (b) One degree of freedom is lost because, when expressed as a deviation from the sample mean, the final deviation in the sample fails to supply information about population variability. (c) Degrees of freedom makes sense only if we wish to estimate some unknown characteristic of a population. (d) Degrees of freedom reflect the poor quality of one or more observations.

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