The range is 7 points and the interquartile range is 2 points from 2. Chapter 4 statistical analysis and interpretation of data 4. Chapter 4 measures of variability flashcards quizlet. Just as in the section on central tendency where we discussed measures of the center of a distribution of scores, in this chapter we will discuss measures of the variability.
As the name implies, the semiinterquartile range is onehalf of the interquartile range range. The terms variability, spread, and dispersion are synonyms, and refer to how spread out a distribution is. It cannot be used with grouped data and it ignores the distribution of intermediate values. Conceptually, the semiinterquartile range measures the distance from the middle of the distribution to the. Because it is completely determined by the two extreme values and ignores the other scores in the distribution. For example, sample a sample b 11 5 12 8 10 14 12 15 15 16 18 17 20 18 22. The index of qualitative variation the range the interquartile rage the standard deviation the variance measures of variability we look at variation and diversity so we can think about the differences between the respondents not just the similarities. Compared with the range, the primary purpose of the interquartile range is to represent the variability. Chapter 4 measures of variability problems page 115. There are three main ways to measure variability in a data set. Dec 05, 2016 chapter 4 measures of variability alexandra springer. Measures of variability are statistical procedures to describe how spread out the data is. This chapter intro duces measures of variability, which are.
It is often desirable to consider measures of variability dispersion, as well as measures of location. The range or difference between the first and third quartiles. Find the error hiroshi was finding the measures of variation of the. The standard deviation is explored in the next section of this guide. Similar to measures of central tendency, there are multiple measures of variability. Andreas artemiou chapter 1 lecture 4 measures of variability.
Choose from 500 different sets of statistics chapter 4 variability flashcards on quizlet. First formula i i d o iqv a measure of variability for nominal variables. Important to randomize order of two treatments and use blinding if possible. A semiquantitative exposure profile may be based on screening samples, bayesian decision analysis, or. Request pdf measures of variability this chapter discusses several.
You should be able to define the terms in the important terms section of this. These formulas are the root formulas for many of the statistical tests that will be covered later. Measures of variability dispersionallow us to summarize our data set with a single value. Information is insufficient in regards to the dispersion i. A qualitative exposure profile is based on professional judgment. This chapter demonstrates ways to use spss to examine variability in a sam ple.
When the interquartile range is used to describe variability, it commonly is transformed into the semiinterquartile range. Specifically, it tells whether the scores lt d l t th are clustered close together or are spread out over a large distance. Another important characteristic of data is variability. Chapter 5 measures of variation kendall hunt higher education. Same center, different variation range the range of a data set is the difference between the largest and smallest data values. Iqr q 3 q 1 i before working with iqr lets see how to calculate q 1 and q 3 and what a boxplot is. Which measures of variation show the girls similarities in their training. Chapter 4 statistics chapter 4 variability chapter. Quartiles are values that divide the data set into four equal parts. In this chapter, we shall concentrate on measures of location, and in particular on measures of central location, which in some way describe the center or the middle of a set of data. Range is defined as the difference between the largest and smallest values.
Monday tuesday wednesday thursday friday saturday sunday lucy 7 mi 3 mi 5 mi 8 mi 6 mi 10 mi 9 mi dena 6 mi 4 mi 6 mi 8 mi 11 mi 9 mi 7 mi c 12. The two statistics of this type that we will examine. Measures of variability numbers that describe diversity or variability in the distribution. Lesson 3 skills practice measures of variation find the. As a descriptive statistic, variability measures the degree to which the scores are spread out or clustered together in a distribution. Measures of variability tell how spread out the observations are, that is, how much the values differ from individual to individual. The range is the difference between the greatest and least data values. In this chapter we discuss five measures of variability.
Measures of variation are used to describe the distribution of the data. Chapter 5 measures of variability 05frankfort 4657. Chapter 4 learning outcomes 1 understand purpose of measuring variability 2 define range and interquartile range 3 compute range and interquartile range 4 understand standard deviation 5 calculate ss, variance, standard deviation of population 6 calculate ss, variance, standard deviation of sample. Measures of central tendency and variability after reading this chapter, you will be able to calculate the three measures of central tendency and the three measures of variability interpret the information conveyed by each measure of central tendency and variability. The range is 27 points and the interquartile range is 2 points from 2. An examination of measures of variation is a logical extension of any description of a data set using the measures of central tendency that we examined in the previous chapter. Measures of variability and central tendency objectives calculate descriptive for continuous and categorical data edit output tables although measures of central tendency and variability were presented as separate chapters in the fundamentals text, they are presented together here because they are.
The next part of this chapter presents and discusses four measures of variability. Variability measures how well an individual score or group of scores represents the entire distribution. A quantitative measure of the degree to which scores in a distribution. In the context of inferential statistics, variability. Chapter 4 chapter 4 measures of variability powerpoint. Variation standard deviation coefficient of variation range variance. Measures boxplot exercises iqr quartiles creating a boxplot iqr i another measure of variability is the interquartile range iqr. Most of the rest of the chapter is spent discussing the most important measures of variability, the variance and the standard deviation.
Variability variability provides a quantitative measure of the degree to which scores in a distribution are spread out or clustered together central tendency and variability central tendency describes the central point of the distribution, and variability describes how the scores are scattered around that central point. Lesson 3 homework practice measures of variation answer key. How much difference to expect from score to score how well the mean represents the scores on the whole how well an individual score. It cannot be used with grouped data and it ignores the. Measures of variation refer to a group of statistics that is intended to provide us with information on how a set of scores are distributed. Matchedpair designs two matched individuals, or same individual, receives each of two treatments. Chapter 4 measures of dispersion business statistics. Variability refers to how spread apart the scores of the distribution are or how much the scores vary from each other.
Sulleza slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. Just as in the section on central tendency where we discussed measures of the center of a distribution of scores, in this chapter we will discuss measures of the variability of a distribution. Lets take a look at the blackboard measures of variability mode median mean another example. Learn vocabulary, terms, and more with flashcards, games, and other study tools. All three measures of the range are used in some circumstances, but they all depend on just two scores. Measures of variability the importance of measuring variability the range iqr interquartile range variance standard deviation considerations for choosing a measure of variation the importance of measuring variability central tendency numbers that describe what is typical or average central in a distribution measures of.
Chapter 4 chapter 4 variability variability definition a. We demonstrate how to calculate range, interquartile range, mean deviation. A measure of variability usually accompanies a measure of central tendency as basic descriptive. Chapter 3 describes the use of spss to obtain measures of location for a data set. This will not happen very often, but here we see an instance where the textbook authors use a different definition than the common definition. Chapter 3 variability learning objectives after reading this chapter, you should be able to do the following. The mean of the squared deviations from the mean of a distribution.
Adjust for having squared all the differences by taking the square root of the variance. Central tendency and variability central tendency describes the central. Learn statistics chapter 4 variability with free interactive flashcards. View test prep chapter 4 from accounting 75431 at city school of law, quetta. However, researchers also need to describe the amount of differences among the scores of a variable. Summary this chapter discusses several measures of variability along with their advantages and disadvantages. Q1 is the score value at or below 25%, and q3 is the score value at or below which 75%. Measures of central tendency and variability 97 we said that the median is a better measure of central tendency when the mean does not do a good job of describing its dataset.
Which measure of variation is greater, the range or the interquartile range. Chapter 4 measures of dispersion learning objectives after studying this chapter, you should be able to provide the importance of the concept of variability dispersion. Explain what the standard deviation measures compute the variance and the standard deviation for a population using a calculator compute the variance and the standard deviation for a sample using a calculator and spss. Variability a quantitative measure of the differences between scores and describes the degree to which scores are spread out or clustered together. Unlike the ranges, these measures of variability take into consideration all of the data. The range is completely determined by the extreme scores. Choose your answers to the questions and click next to see the next set of questions. Find the measures of variability and any outliers for each set of data. This video series was created several years ago for an graduate level introductory statistical methods course. Measures of variability statistical applications for the behavioral.
Measures of variation and some other kinds of statistical descriptions will be discussed in next chapter. Measures of variability are very useful tools for determining the relative position of an individual score in a distribution and for describing the dispersion of the data. Variability variability serves both as a descriptive measure and as an important component of most inferential statistics. Chapter 4 summarizing scores with measures of variability.
Chapter 4 measures of central tendency and variability. The mean of the squared deviations from the mean of. Strengths and weaknesses of the interquartile range. Variability serves both as a descriptive measure and as an important component of most inferential statistics. Central tendency and variability chapter 4 measures of central tendency 2. In the context of inferential statistics, variability provides a measure of how. Statistical applications for the behavioral and social sciences, pp. If research participants do not agree about the mean ing of key terms and phrases, it is difficult to combine or com. Measures of variability data the sample variance, s2 from a sample of n observations, x 1, x 2,x n, the sample variance is given by why divide by n 1. Measures of central tendency locate only the center of a distribution of measures. Compared with the range, the primary purpose of the interquartile range is to represent the variability in a set of data while lessening the influence of outliers. Variability the goal for variability is to obtain a measure of how spread out the scores are in a distribution. Outliers use the interquartile range to identify any outliers in.
There are four major measures of variability, including the range, interquartile range, variance, and standard deviation. Variability variability the goal for variability is to obtain a measure of how spread out the scores are in a distribution. The range the range of a set of numerical data is the difference between the highest and the lowest values. A single very large or very small value would give a misleading impression of the spread of the data. Variability recognizes that not all of the scores are the same, there are differences unless there is zero variability, and then measures how big the differences are. Chapter 4 measures of variability powerpoint lecture slides essentials of statistics for the behavioral sciences eighth edition by frederick j gravetter and larry b. Measures of variability in statistics by mary krystle dawn d. Chapter 4 summarizing scores with measures of variability variability and the standard deviation the concept of variability is easily introduced by presenting the class with two samples that have the same mean but drastically different standard deviations. In this chapter, we discuss five measures of variability. A characterization of the daytoday variability of exposures of a seg. Just as in the section on central tendency where we discussed measures of the. Chapter 4 statistical analysis and interpretation of data.
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