![]() Interpreting a contingency table is easier when the raw data is converted to percentages. Number of visits to the library in the past year You read “across” the table to see how the independent and dependent variables relate to each other. Usually, an independent variable (e.g., gender) appears along the vertical axis and a dependent one appears along the horizontal axis (e.g., activities). In a contingency table, each cell represents the intersection of two variables. Multivariate analysis is the same as bivariate analysis but with more than two variables. You can also compare the central tendency of the two variables before performing further statistical tests. In bivariate analysis, you simultaneously study the frequency and variability of two variables to see if they vary together. If you’ve collected data on more than one variable, you can use bivariate or multivariate descriptive statistics to explore whether there are relationships between them. Likewise, while the range is sensitive to outliers, you should also consider the standard deviation and variance to get easily comparable measures of spread. If you were to only consider the mean as a measure of central tendency, your impression of the “middle” of the data set can be skewed by outliers, unlike the median or mode. Programs like SPSS and Excel can be used to easily calculate these. It’s important to examine data from each variable separately using multiple measures of distribution, central tendency and spread. Univariate descriptive statistics focus on only one variable at a time. Variance of visits to the library in the past year Data set: 15, 3, 12, 0, 24, 3 To find the variance, simply square the standard deviation. The more spread the data, the larger the variance is in relation to the mean. Variance reflects the degree of spread in the data set. The variance is the average of squared deviations from the mean. Raw dataįrom learning that s = 9.18, you can say that on average, each score deviates from the mean by 9.18 points. Standard deviations of visits to the library in the past yearIn the table below, you complete Steps 1 through 4. Find the square root of the number you found.Divide the sum of the squared deviations by N – 1.Subtract the mean from each score to get the deviation from the mean.There are six steps for finding the standard deviation: The larger the standard deviation, the more variable the data set is. It tells you, on average, how far each score lies from the mean. The standard deviation ( s or SD) is the average amount of variability in your dataset. Range of visits to the library in the past year Ordered data set: 0, 3, 3, 12, 15, 24 To find the range, simply subtract the lowest value from the highest value. The range gives you an idea of how far apart the most extreme response scores are. The range, standard deviation and variance each reflect different aspects of spread. Measures of variability give you a sense of how spread out the response values are. Mode number of library visits Ordered data setįind the most frequently occurring response: 3 To find the mode, order your data set from lowest to highest and find the response that occurs most frequently. A data set can have no mode, one mode, or more than one mode. The modeis the simply the most popular or most frequent response value. Now you can use descriptive statistics to find out the overall frequency of each activity (distribution), the averages for each activity (central tendency), and the spread of responses for each activity (variability). Your data set is the collection of responses to the survey. You distribute a survey and ask participants how many times they did each of the following in the past year: Research exampleYou want to study the popularity of different leisure activities by gender. You can apply these to assess only one variable at a time, in univariate analysis, or to compare two or more, in bivariate and multivariate analysis. The variabilityor dispersion concerns how spread out the values are.The central tendencyconcerns the averages of the values.The distribution concerns the frequency of each value.There are 3 main types of descriptive statistics: Frequently asked questions about descriptive statistics.
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