First, adding a negative number is the same as subtraction. For nominal level variables, construction of the frequency distribution is typically very straightforward. You might also want to use this section as an opportunity to become more familiar with your calculator. The mathematical characteristic of a variable and the major criterion for selecting statistical techniques. I am consistently impressed by the sensitivity of my colleagues to the needs of the students, and, for their assistance in preparing this edition, I would like to thank Marion Manton, Christopher Newport University; Dennis Berg, California State University, Fullerton; Bradley Buckner, Cheyney University of Pennsylvania; Kwaku Twumasi-Ankrah, Fayetteville State University; Craig Tollini, Western Illinois University; H.
Statistical analysis is relevant only for research projects in which information is represented as numbers. We will examine each situation separately. May not contain Access Codes or Supplements. To minimize the probability of rejecting a null hypothesis that is in fact true, use very low alpha levels. Note the negative sign: it means that the death rate has decreased by 50%. Finally, I want to acknowledge the support of my family and rededicate this work to them.
Computing percentages eliminates the size difference of the two campuses by standardizing both distributions to the base of 100. To test the contact hypothesis, we would begin with people from different racial or ethnic groups. Note that the number of permitted mathematical operations increases as we move from nominal to ordinal to interval-ratio levels of measurement. Construct pie and bar charts to display the distributions of sex, support for gun control, and level of education. The 2000 rate would have been half the size of the 1995 rate. Any failings contained in the text are, of course, my responsibility and are probably the results of my occasional decisions not to follow the advice of my colleagues. If you are patient with yourself and work through them step by step, beginning with the parenthetical expression, even the most imposing formulas can be managed.
The unfortunate but unavoidable truth is that a single course in statistics will not close the gap entirely. The numerical codes for the variables are as follows. There is nothing magical about data and statistics. It is obvious that the 2001 percentage is much higher, and calculating the percentage change will give us an exact idea of the magnitude of the change. On the other hand, inappropriate statistical applications can limit the usefulness of an otherwise carefully done project.
To illustrate the usefulness of frequency distributions and to provide some data for examples, assume that the counseling center at a university is assessing the effectiveness of its services. If we asked respondents to list their exact income in dollars, we will generate scores that are interval-ratio in level of measurement. Since the cumulative percentage column is clearer and easier to interpret in such cases, it is normally preferred to the cumulative frequencies column. If there is a single negative number in the calculations, the answer will be negative. To construct frequency distributions for interval-ratio level variables, you must decide how many categories to use and how wide these categories should be. In this chapter, we will consider some commonly used techniques for presenting research results: percentages and proportions; ratios and rates; percentage change. The critical region includes all unlikely or rare sample outcomes.
To be sure, computers and calculators have made computation less of an issue today. Category: Arabic alphabet Author : Robert B. Describe the limited but crucial role of statistics in social research. A supervisor in the solid waste management division of a city government is attempting to assess two different methods of trash collection. Do the scores still make sense? This chart would be interpreted in exactly the same way as the pie chart in Figure 3. Research is a disciplined inquiry that can take numerous forms. If we argued that prejudice was the result of low levels of education, the words the result of tells us that prejudice is a dependent variable and education is an independent variable.
To change the size of the output window, click the middle symbol shaped like either a square or two intersecting squares in the upperright-hand corner of the Output window. Census data is readily available at www. Given the level of precision of the measurement in years, as opposed to 10ths or 100ths of a year , no case could have a score falling between these class intervals. Include a column for percentages. While we would be primarily focused on assessing our theory, we would also look for other trends in the data. Percentages or proportions could have been used to summarize the overall distribution e. For example, try to ascertain the general level of satisfaction of the students from Table 2.
There are many other programs that are probably available to you that will help you accomplish the goal of generating accurate statistical results with a minimum of effort and time. Suppose we had a set of three scores: 10, 12, and 13. . The researcher also gathers data on age and major to see if there is any connection between these variables and frequency of sexual harassment. Nominal variables are rudimentary, but there are criteria and procedures that we need to observe in order to assure adequate measurement. The scores years must be grouped into larger categories to heighten clarity and ease of comprehension. They provide the scientist with some of the most useful techniques for evaluating hypotheses and testing theory.