Mean deviation and Standard deviation. (1) It requires the mean to be the measure of central tendency and therefore, it can only be used with interval data, because ordinal and nominal data does not have a mean. In both positive and negative skewed cases median will be preferred over mean. Alow standard deviation scoreindicates that the data in the set are similar (all around the same value like in the data set A example above). Hence range cannot be completely representative of the data as all other middle values are ignored. what are the disadvantages of standard deviation? Positive Skewness: means when the tail on the right side of the distribution is longer or fatter. Therefore, the result can only be influenced with changes in those two values, not by any other value of the variable. Web5 Advantages and disadvantages. Therefore, the Range = 12 1 = 11 i.e. It is used to compare the degree of variation between two or more data series that have different measures or values. This is a weakness as it would make data analysis very tedious and difficult. ), Consider the following table of scores:SET A354849344240SET B32547507990. Advertisement cookies are used to provide visitors with relevant ads and marketing campaigns. Compare the advantages and disadvantages of each one and, from your own thinking, write down an instance of when each one would be appropriate to use. Population variance (2) tells us how data points in a specific population are spread out. Moreover, biofilms are highly (c) In usual situations, it is calculated taking deviations from the easily computable arithmetic mean of the given observations on the variable. Moreover, the results of the absolute measure gets affected by the number of observations obtainable on the given variable as they consider only the positive differences from their central value (Mean/Median). Thus, the distribution of most people will be near the higher extreme, or the right side. This mean score (49) doesnt appear to best represent all scores in data set B. WebThe benefits of the Gini coefficient are described as: mean independence (if all incomes were doubled, the measure would not change), population size independence (if the population were to change, the measure of inequality should not change, all else equal), symmetry (if any two people swap incomes, there should be no change in the measure of Indeed, bacteria in biofilm are protected from external hazards and are more prone to develop antibiotic resistance. If outliers are present it may give a distorted impression of the variability of the data, since only two observations are included in the estimate. The table represented above shows that the poorest 20 per cent of the income earners receive only 5 per cent of the total income whereas the richest 20 per cent of the sample respondents shared as much as 43 per cent of it. Defined as the difference In particular, if the standard deviation is of a similar size to the mean, then the SD is not an informative summary measure, save to indicate that the data are skewed. The Range, as a measure of Dispersion, has a number of advantages and disadvantage. Divide the sum in #4 by (n 1). 5. This concept of dispersion in statistics helps in the understanding of the distribution of data. The extent of dispersion increases as the divergence between the highest and the lowest values of the variable increases. For all these reasons. (a) The main complaint against this measure is that it ignores the algebraic signs of the deviations. Again, in the case of a complex distribution of a variable with respective frequencies, it is not much easy to calculate the value of Range correctly in the above way. WebExpert Answer. Analytical cookies are used to understand how visitors interact with the website. Cookie Policy - Terms and Conditions - Privacy Policy, AP Statistics: Percentiles, Quartiles, z-Scores (measures of position). WebExpert Answer. Table 1 Calculation of the mean squared deviation. Evaluation of using Standard Deviation as a Measure of Dispersion (AO3): (1) It is the most precise measure of dispersion. The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional". The usual Relative Measures of Dispersion are: Among these four coefficients stated above the Coefficient of Variation is widely accepted and used in almost all practical situations mainly because of its accuracy and hence its approximation to explain the reality. Statisticians together unanimously opines that an ideal measure of dispersion should possess certain necessary characteristics. Negative Skewness is when the tail of the left side of the distribution is longer or fatter than the tail on the right side. Exam Tip:Be careful when reading tables that have a SD. The statisticians here prescribe for an well-known concept dispersion or the scatteredness or variability of the values of the variable usually from their arithmetic mean. Lorenz Curve The curve of concentration: Measurement of Economic Inequality among the Weavers of Nadia, W.B: This cookie is set by GDPR Cookie Consent plugin. Squaring these numbers can skew the data. (c) It is rarely used in practical purposes. In the Algebraic method we split them up into two main categories, one is Absolute measure and the other is Relative measure. The values that divide each part are called the first, second, and third quartiles; and they are denoted by Q1, Q2, and Q3, respectively. Advantages: The Semi-interquartile Range is less distorted be extreme scores than the range; Disadvantages: It only relates to 50% of the data set, ignoring the rest of the data set; It can be laborious and time consuming to calculate by hand; Standard Deviation This measure of dispersion is normally used with the mean as the measure of central WebStart studying Year 1: Statistics Ch 2- Measures of location an spread. This will always be the case: the positive deviations from the mean cancel the negative ones. Additionally, the content has not been audited or verified by the Faculty of Public Health as part of an ongoing quality assurance process and as such certain material included maybe out of date. It is not used much in statistical analysis, since its value depends on the accuracy with which the data are measured; although it may be useful for categorical data to describe the most frequent category. 3. The quartiles are calculated in a similar way to the median; first arrange the data in size order and determine the median, using the method described above. Range only considers the smallest and largest data elements in the set. Through this measure it is ensured that at least 50% of the observations on the variable are used in the calculation process and with this method the absolute value of the Quartile Deviation can easily be measured. You may have noticed that you see a rainbow only when you look away from the Sun. It can be found by mere inspection. *can be affected by Disadvantages. WebAdvantages and disadvantages of the mean and median. When we use the Arithmetic mean instead of the Median in the process of calculation, we get a rough idea on the nature of distribution of the series of observations given for the concerned variable. (d) The algebraic treatment used in the process should easily be applicable elsewhere. 1. WebAssignment 2: List the advantages and disadvantages of Measures of Central Tendency vis a vis Measures of Dispersion. This website uses cookies to improve your experience while you navigate through the website. A third measure of location is the mode. The dotted area depicted above this curve indicates the exact measure of deviation from the line of Absolute-Equality (OD) or the Egalitarian-Line (dotted Line) and hence gives us the required measure of the degree of economic inequality persisting among the weavers of Nadia, W.B. WebMerits of Range: (1) Range is rigidly defined. Uses The measure of dispersion is categorized as: (i) An absolute measure of dispersion: The measures express the scattering of observation in terms of distances i.e., range, quartile deviation. KSSM MATHEMATICS FORM 4Measures of Dispersion for Ungrouped DataAdvantages and disadvantages of various measures of dispersionExample 10 Example 11Page 224(Live version)Please post your math-related questions here:https://www.messenger.com/t/olzenmathsMy Facebook PageOlzen Mathematics 2020https://www.facebook.com/olzenmaths/SPM Mathematics Revisionhttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5vjES5ilKAmpqxnr_ksmD0nhttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5vq6Gvr7XxTA74pGo2tnv2hhttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5tibouEfmmJMxVpepXTVO7ASPM Trial 2019 Mathematics (Penang)https://www.youtube.com/playlist?list=PLkQXp7Lpcc5sen1xdtmUOeBCnWUkQo6tlKBSM Mathematics Form 4 The Straight Linehttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5uRnZeuuLmeH2uCRvsI1FWTSetshttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5tCU4z6cHRyb8edITHnlz4dMathematical Reasoninghttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5tHoLE6SmXeMgJLfR-ppfLJKBSM Mathematics Form 5Chapter 1: Number Baseshttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5uM44q_Lh9qvTMlP37z48i_Chapter 3: Transformations IIIhttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5vsAJJYlJNnhYS8uMSWPLr8Chapter 4: Matriceshttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5uFlFo3EAQaQO8FzKLVEltZChapter 5: Variationshttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5uWR1FgOFS3I0659p1KiAIiChapter 6: Gradient and Area under a Graphhttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5uLywl9PNUk7L3vKn1Q94kRChapter 7: Probability IIhttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5vY4Qk6YKlhgt2RJnh49_uwChapter 8: Bearinghttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5sCBEcZtLLeRbCjMBN0WsQwChapter 9: Earth as a Spherehttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5sPJiCh5HrCyEsfTn9C0qfIChapter 10: Plans and Elevationshttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5trEPI6kI7qGIuyKq_qSVNFKSSM Mathematics Form 4Chapter 1: Quadratic Functions and Equations in One Variablehttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5uuLRIaZvhC6c7wy2Y2wAQxChapter 2: Number Baseshttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5uM44q_Lh9qvTMlP37z48i_Chapter 3: Logical Reasoninghttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5tW1FV9X0xuJiIoJWPzmR47Chapter 4: Operations on Setshttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5t-vZJwjM-SwwHlnPXN3Y3aChapter 5: Network in Graph Theoryhttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5sC3Ou4Z9_C1Mzc1AFLPbkCChapter 6: Linear Inequalities in Two Variableshttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5tOjdt-dYMSGrjNXplO9zEqChapter 7: Graphs of Motionhttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5sEQG0GawrUUABSN9vF-nT5Chapter 8: Measures of Dispersion for Ungrouped Datahttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5uSKEYCI0cfnU4OWTtpaLrWChapter 9: Probability of Combined Eventshttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5sAEsiFLHqo8ppw-D4oZo4Jhttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5vY4Qk6YKlhgt2RJnh49_uwChapter 10: Consumer Mathematics: Financial Managementhttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5sR0fJUZSsbU7eh7X9kmT54Additional MathematicsLinear Programminghttps://www.youtube.com/playlist?list=PLkQXp7Lpcc5vZk4_ncie9c6fqgCf_Fhn3 Web2. Consider x to be a variable having n number of observations x1, x2, x3, . If the skewness is between -0.5 and 0.5, the data are fairly symmetrical. Huang et al. Exclusive offers can be provided to our target group via direct mail, allowing us to personalize the buying There are four key measures of dispersion: Range. How much wire would one need to link them? obesity or high blood pressure) and in this case the distributions are usually unimodal. Revision Note:In your exam, you will not be asked to calculate theStandard Deviationof a set of scores. In order to understand what you are calculating with the variance, break it down into steps: Step 1: Calculate the mean (the average weight). 2.22, 2.35, 2.37, 2.40, 2.40, 2.45, 2.78. 6. This is a weakness as the standard deviation does not cover all data types within its use and therefore is limited with regards to its use. Note that the text says, there are important statistical reasons we divide by one less than the number of data values.6. We thus express the magnitude of Range as: Range = (highest value lowest value) of the variable. As the components of CV, we are to derive first the Mean and the Standard Deviation of the scores obtained by the two Batsmen separately using the following usual notations: Let us prepare the following table for finding out Mean and SD of the given information: For the cricketer S the Coefficient of Variation is smaller and hence he is more consistent. What are the advantages and disadvantages of arithmetic mean? They are liable to yield inappropriate results as there are different methods of calculating the dispersions. If you have any concerns regarding content you should seek to independently verify this. It is the sharpness of the peak of a frequency-distribution curve.It is actually the measure of outliers present in the distribution. Measures of dispersion give you an indication of the spread of your data; the range and standard deviation are two key examples. They are liable to misinterpretations, and wrong generalizations by a statistician of based character. Measures of dispersion provide information about the spread of a variable's values. It also means that researchers can spend more time interpretating and drawing inferences from the data as oppose to calculating and analysing. It can be shown that it is better to divide by the degrees of freedom, which is n minus the number of estimated parameters, in this case n-1. a. Moreover, these measures are not prepared on the basis of all the observations given for the variable. Learn vocabulary, terms, and more with flashcards, games, and other study tools. When describing the scores on a single variable, it is customary to report on both the central tendency and the dispersion. Advantage 1: Fast and easy to calculate. The Range is the difference between the largest and the smallest observations in a set of data. Range Defined as the difference between the largest and smallest sample values. This will make the tail of the distribution longer towards the left side or the lower side, and the less values (low ages) will shift the mean towards the left, making it a negatively skewed distribution. Here lies the superiority of the Relative Measures over the Absolute Measures of dispersion. Range: The simplest and the easiest method of measuring dispersion of the values of a variable is the Range. As stated above, the range is calculated by subtracting the smallest value in the data set from the largest value in the data set. Exception on or two, of the methods of dispersion involve complicated process of computation. But the merits and demerits common to all types of measures of dispersion are outlined as under: Copyright 2014-2023 Statistical models summarize the results of a test and present them in such a way that humans can more easily see and understand any patterns within the data. 2.1 Top-Down Approach. a. Statisticians use variance to see how individual numbers relate to each other within a data set, rather than using broader mathematical techniques such as arranging numbers into quartiles. It holds for a large number of measurements commonly made in medicine. It is a common misuse of language to refer to being in the top quartile. However, the interquartile range and standard deviation have the following key difference: The interquartile range (IQR) is not affected by extreme outliers. Give a brief and precise report on this issue. Measures of Dispersion or Variability. *it only takes into account the two most extreme values which makes it unrepresentative. (g) Statisticians very often prescribe SD as the true measure of dispersion of a series of information. 1.81, 2.10, 2.15, 2.18. (b) It is not generally computed taking deviations from the mode value and thereby disregards it as another important average value of the variable. Expert Answer Meaning of Dispersion: Dispersion is the extent to which values in a distribution differ from the average of the distribution. The range is the difference But, the results of such measures are obtained in terms of the units in which the observations are available and hence they are not comparable with each other. Web1. (c) It is least affected by sampling fluctuations. You may however be asked to interpret a standard deviation value (explain to the examiner what the measure means). Medical Statistics: a Commonsense Approach 4th ed. To study the exact nature of a distribution of a variable provided with a number of observations on it and to specify its degree of concentration (if any), the Lorenz Curve is a powerful statistical device. that becomes evident from the above income distribution. If the data points are further from the mean, there is a higher deviation within the data set; thus, the more spread out the data, the higher the standard deviation. In a set of data that has many scores this would take a great deal of time to do. Characteristics of an ideal If outliers exist in a set of data such that the lowest or highest extremes are far away from almost every other data element in the set, then range may not be the best way to measure dispersion. For example, height might appear bimodal if one had men and women on the population. Share Your PDF File
Its not quite the same as the number of items in the sample. Webadvantages and disadvantages of measures of central tendency and dispersion from publication clinicians guide to statistics for medical out is called the measure of dispersion web 29 nov 2021 measures of central tendency class 11 economics mcqclass 11 Wide and dynamic range. The first step in the creation of nanoparticles is the size Merits and Demerits of Measures of Dispersion. Calculation for the Coefficient of Mean-Deviation. Without statistical modeling, evaluators are left, at best, with eye-ball tests or, at worst, gut-feelings of whether one system performed better than another. It is measured as= (highest value lowest value) of the variable. Square each deviation from the mean.4. * You can save and edit ideas which makes it easier and cheaper to modify your design as you go along. The necessity is keenly felt in different fields like economic and business analysis and forecasting, while dealing with daily weather conditions, etc. When would you use either? This makes the tail of extreme values (high income) extend longer towards the positive, or right side. Mean is rigidly defined so that there is no question of misunderstanding about its meaning and nature. It is the degree of distortion from the symmetrical bell curve or the normal distribution.It measures the lack of symmetry in data distribution . To study the extent or the degree of economic inequality prevailing among the people of various professional categories, construction of a Lorenz Curve and estimation of the Gini Co-efficient is the order of the day as it helps the planners to take effective future development policies for the people indiscriminately. Measures of location describe the central tendency of the data. WebClassification of Measures of Dispersion. Lets Now Represent It in a Diagramitically . The cookies is used to store the user consent for the cookies in the category "Necessary". They facilitate in making further statistical analysis of the series through the devices like co-efficient of skewness, co-efficient of correlation, variance analysis etc. For example, if one were to measure a students consistency on quizzes, and he scored {40, 90, 91, 93, 95, 100} on six different quizzes, the range would be 60 points, marking considerable inconsistency. This is a Here, we have plotted these information on a two dimensional plane showing percentage of income-classes horizontally and the corresponding percentage of income received vertically. Privacy Policy3. When there is an even number of values, you count in to the two innermost values and then take the average. Note the mean of this column is zero. The variance is mathematically defined as the average of the squared differences from the mean. The drawback of variance is that it is not easily interpreted. For any Sample, always the sum of deviations from mean or average is equal to 0. The result finally obtained (G=0.60) thus implies the fact that a high degree of economic inequality is existing among the weavers of Nadia, W.B. Their calculation is described in example 1, below. Outliers are single observations which, if excluded from the There are no constraints on any population. Further algebraic treatments can also be applied easily with the result obtained afterwards. Allow Necessary Cookies & Continue (c) It is not a reliable measure of dispersion as it ignores almost (50%) of the data. It indicates the lacks of uniformity in the size of items. The measure of dispersion is categorized as: (i) An absolute measure of dispersion: The measures express the scattering of observation The standard deviation is a statistic that measures the dispersion of a dataset relative to its mean and is calculated as the square root of the variance. Low kurtosis in a data set is an indicator that data has lack of outliers. Standard Deviation: The concept of SD as a successful measure of dispersion was introduced by the renowned statistician Karl Pearson in the year 1893 and it is still recognised as the most important absolute measure of dispersion. Statistically speaking, it is a cumulative percentage curve which shows the percentage of items against the corresponding percentage of the different factors distributed among the items. The standard deviation of a sample (s) is calculated as follows: \(s = \;\sqrt {\frac{{\sum {{\left( {{x_i} - \bar x} \right)}^2}}}{{n - 1}}}\). Some of our partners may process your data as a part of their legitimate business interest without asking for consent. Disclaimer Copyright, Share Your Knowledge
Advantages of Coefficient of Variation 1. This website includes study notes, research papers, essays, articles and other allied information submitted by visitors like YOU. The calculation of the standard deviation is described in Example 3. Step 2: Subtract the mean and square the result. Consider a sample of sizen , and there is always constraint on every sample i.e. Measures of Location and Dispersion and their appropriate uses, 1c - Health Care Evaluation and Health Needs Assessment, 2b - Epidemiology of Diseases of Public Health Significance, 2h - Principles and Practice of Health Promotion, 2i - Disease Prevention, Models of Behaviour Change, 4a - Concepts of Health and Illness and Aetiology of Illness, 5a - Understanding Individuals,Teams and their Development, 5b - Understanding Organisations, their Functions and Structure, 5d - Understanding the Theory and Process of Strategy Development, 5f Finance, Management Accounting and Relevant Theoretical Approaches, Past Papers (available on the FPH website), Applications of health information for practitioners, Applications of health information for specialists, Population health information for practitioners, Population health information for specialists, Sickness and Health Information for specialists, 1. specially in making predictions for future purposes. This undoubtedly depicts a clear picture of high degree of income- inequality prevailing among our sample respondents. The usual measures of dispersion, very often suggested by the statisticians, are exhibited with the aid of the following chart: Primarily, we use two separate devices for measuring dispersion of a variable. This is because we are using the estimated mean in the calculation and we should really be using the true population mean. (d) To compute SD correctly, the method claims much moments, money and manpower. Dispersion is the degree of scatter of variation of the variables about a central value. We also share information about your use of our site with our social media, advertising and analytics partners who may combine it with other information that youve provided to them or that theyve collected from your use of their services. (a) Quartile Deviation is easy to calculate numerically. (d) It is easy to calculate numerically and simple to understand. The major advantage of the mean is that it uses all the data values, and is, in a statistical sense, efficient. It does not necessarily follow, however, that outliers should be excluded from the final data summary, or that they always result from an erroneous measurement. Dispersion is the degree of scatter of variation of the variables about a central value. They are liable to misinterpretations, and wrong generalizations by a The median is defined as the middle point of the ordered data. Degree of Degrees of freedom of an estimate is the number of independent pieces of information that went into calculating the estimate. what are the advantages of standard deviation? The interquartile range is a useful measure of variability and is given by the lower and upper quartiles. Toggle Advantages and disadvantages subsection 5.1 Advantages. Bacteria in the human body are often found embedded in a dense 3D structure, the biofilm, which makes their eradication even more challenging. Variance is measure to quantify degree of dispersion of each observation from mean values. The Standard Deviation, as a complete and comprehensive measure of dispersion, is well accepted by the statisticians specially because it possesses simultaneously all the qualities unhesitatingly which are required for an ideal measure of dispersion. We need to find the average squared deviation. Outlier is a value that lies in a data series on its extremes, which is either very small or large and thus can affect the overall observation made from the data series. Sum the squares of the deviations.5. By clicking Accept, you consent to the use of ALL the cookies. 2.1 Top-Down Approach. Next add each of the n squared differences. (c) It can be used safely Homework1.com. Leptokurtic (Kurtosis > 3) : Peak is higher and sharper than Mesokurtic, which means that data has heavy outliers. (i) Calculate mean deviation about Arithmetic Mean of the following numbers: Let us arrange the numbers in an increasing order as 15, 30, 35, 50, 70, 75 and compute their AM as: AM = 15 + 30 + 35 + 50 + 70 + 75/6 = 275/6. Mesokurtic : This distribution has kurtosis statistic similar to that of the normal distribution. Disadvantages of Coefficient of Variation 1. The quartiles, namely the lower quartile, the median and the upper quartile, divide the data into four equal parts; that is there will be approximately equal numbers of observations in the four sections (and exactly equal if the sample size is divisible by four and the measures are all distinct). They, by themselves, cannot give any idea about the symmetricity, or skewed character of a series. Every score is involved in the calculation and it gives an indication of how far the average participant deviates from the mean. If we are provided with homogeneous or equivalent observations on two or more but not on unlimited number of variables with their own standard deviations, we can easily derive their combined standard deviation. The median is the average of the 9th and 10th observations (2.18+2.22)/2 = 2.20 kg. The prime advantage of this measure of dispersion is that it is easy to calculate. An example of data being processed may be a unique identifier stored in a cookie. For all these reasons the method has its limited uses. Determine the Coefficient of Range for the marks obtained by a student in various subjects given below: Here, the highest and the lowest marks are 52 and 40 respectively. Let us consider two separate examples below considering both the grouped and the ungrouped data separately. The main disadvantage of the mean is that it is vulnerable to outliers. Let us offer a suitable example of it to measure such a degree of income inequality persisting among the weavers of Nadia, W.B. (a) It involves complicated and laborious numerical calculations specially when the information are large enough. Compute the mean.2. as their own. Share Your PPT File. We use cookies to personalise content and ads, to provide social media features and to analyse our traffic. If the x's were widely scattered about, then s would be large. On the other hand, direct mail canbe easily disregarded and is potentially expensive. WebBacterial infections are a growing concern to the health care systems. The below mentioned article provides a close view on the measures of dispersion in statistics. Due to the possibility that (on occasion) measures of central tendency wont be the best way for a number to represent a whole data set, it is important to present a measure of dispersion alongside a measure of central tendency. In the process of variable selection, we can look at those variable whose standard deviation is equal to 0 and we can ignore such independent variables. In this way, s reflects the variability in the data. Thus, it is a positively skewed distribution. Q1 is the middle value in the first half of the rank-ordered data set. For the data presented with their respective frequencies, the idea is to measure the same as the difference between the mid-values of the two marginal classes. WebDirect mail has the advantage of being more likely to be read and providing information in a visual format that can be used at the convenience of the consumer. While making any data analysis from the observations given on a variable, we, very often, observe that the degree or extent of variation of the observations individually from their central value (mean, median or mode) is not the same and hence becomes much relevant and important from the statistical point of view. The result will not be affected even when the distribution has an open end.
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