1 HDFS Methods Review Guide Created by Amanda Leggett and Jennifer Morack Fall 2011 Are you in 400 level classes but have forgotten some of your 312W basics? This guide is for you! Table of Contents: 1. APA style A. Citations 2 B. Format of empirical research articles..6 C. How to do a library search.7 2. Sampling Key Terms.10 3. Empirical Design A. Experimental vs. Correlational..11 B. Cross-Sectional vs. Longitudinal..11 C. Qualitative vs. Quantitative...12 4. Descriptive Statistics A. Frequency Distributions and Histograms.12 B. Measures of Central Tendency..13 C. Measures of Dispersion/Variability 13 5. Inferential Statistics A. Statistical Significance and Hypothesis Testing 13 B. Statistical Tests...14 6. Critical Thinking...16
2 1. APA STYLE A. Citations Why do we use APA style? 1. To aid readers in finding our references. 2. To provide an efficient way of organizing information that others in the field will understand. 3. To avoid plagiarism. Citing Sources In-Text When you draw from the ideas of others, you need to cite the source in the body of the text. This can be done in two ways: (a) incorporate the surname(s) of the author(s) and year of publication as part of the narrative, or (b) place the surname of the author(s) and the year of publication in parentheses at the end of a sentence. Examples of each follow. One Author: Markman (1991) found that marital discord can lead to constructive resolution of conflict. Couples have lower rates of divorce and marital violence after problem-solving intervention (Markman, 1991). Two Authors: Harris and Marmer (1996) reported that fathers in poor families are less involved with their adolescent children than fathers in non-poor families. Fathers in poor families are less likely to spend time with their adolescent children than fathers in non-poor families (Harris & Marmer, 1996).
3 Three to Five Authors: For articles with three to five authors, write out the last names of all of the authors the first time the article is cited in your paper. Every time after that, cite the first author s surname followed by the abbreviation et al. along with the publication date. First time cited in text: Abernathy, Massad, and Romano-Dwyer (1995) reported that female adolescents with low self-esteem are more likely to smoke than their peers with high self-esteem. Research suggests that low self-esteem is one reason teenage girls are motivated to smoke (Abernathy, Massad, & Romano-Dwyer, 1995). Subsequent times cited in text: Abernathy et al. (1995) also examined the association between smoking and selfesteem in male adolescents. For male adolescents, there is no association between smoking and self-esteem, suggesting gender-specific motivations for initiating smoking in adolescence (Abernathy et al., 1995). Six or More Authors: When an article has six or more authors, use et al. the first and every subsequent time you cite the article. Multiple Works within the Same Parentheses:
4 Studies on the same topic or with similar findings can be referenced as a series. If works are by the same author(s), put them in order of year of publication with commas to separate citations. Mio and Willis (2003, 2005) found Past research indicates (Mio & Willis, 2003, 2005) If two or more works by different authors are cited within the same parentheses, put them in alphabetical order and separate citations by semicolons. Investigation of families in economic distress consistently report that girls react with internalization problems whereas boys respond with externalization problems (Conger, Ge, Elder, Lorenz, & Simons, 1994; Flanagan & Eccles, 1993; Lempers, Clark-Lempers, & Simons, 1989). Reference Page This page must contain all the articles that you cite in your paper. The list should be double spaced, with a hanging indent, and in alphabetical order by first author s last name. Format for Journal Articles Last name, Initials., Last name, Initials., & Last name, Initials. (Year). Article name. Journal Name, Volume, first page last page. One Author: Altabe, M. M. (1998). Ethnicity and body image: Quantitative and qualitative analysis. The International Journal of Eating Disorders, 23, 153-159. Two to Seven Authors:
5 Cachelin, F. M., Rebeck, R. M., Chung, G. H., & Pelayo, E. (2002). Does ethnicity influence body-size preference? A comparison of body image and body size. Obesity Research, 10, 158 166. Eight or More Authors: Gilbert, D. G., McClernon, J. F., Rabinovich, N. E., Sugai, C., Plath, L. C., Asgaard, G.,... Botros, N. (2004). Effects of quitting smoking on EEG activation and attention last for more than 31 days and are more severe with stress, dependence, DRD2 A1 allele, and depressive traits. Nicotine and Tobacco Research, 6, 249-267. Format for Books Book: Mitchell, T. R., & Larson, J. R., Jr. (1987). People in organizations: An introduction to organizational behavior (3 rd ed.). New York: McGraw-Hill. Article or Chapter in Edited Book: Bjork, B. A. (1989). Retrieval inhibition as an adaptive mechanism in human memory. In H. L. Roediger III & F. I. M. Craik (Eds.), Varieties of memory & consciousness (pp. 309-330). Hillsdale, NJ: Erlbaum. More Information American Psychological Association (2009). Publication manual of the American Psychological Association (6 th ed.). Washington, DC: American Psychological Association.
6 B. Format of Empirical Research Articles Understanding the format of a journal article Abstract An overview of the entire project Introduction Background on previous, related research; description of the researcher s hypothesis Method Description of participants, materials, and procedure Results Presentation of data and statements of what the researchers discovered Discussion Conclusions and implications based on the results Cycle of Science- In Relation to an Empirical Article
7 Questions to Ask When Reading a Research Article Introduction: 1) What is the general topic of the article? 2) What do we know from previous research? 3) What is the research question? 4) What are the specific research hypotheses? Method: 1) Who were the participants (how many and characteristics)? 2) How were participants sampled and where are they from? 3) What are the main variables and how they operationalized? 4) What was the design of the study and the procedures used? Results: 1) What statistical tests were used? 2) What were the main findings? Discussion: 1) Do the results support the hypothesis and what do they mean? 2) How do these findings relate to past research? 3) What are the implications of the results (or the significance)? 4) What are the limitations of the study? 5) Are there alternative explanations for the findings? C. How to do a Library Search Using PsycInfo I. Searching for relevant articles Go to the PSU Library Website: http://www.libraries.psu.edu Click on Research, then click on Databases by Title (A-Z) Click on P, then scroll down to PsycInfo Database: PsycInfo 1872-current If you are off-campus, login with your Penn State username and password
8 You should automatically be directed to Advanced Search. If not, click on it. Advanced Search Tab: Find articles using up to 3 keywords/authors o Using the pull-down menu on the right, to indicate the type of search terms you are using (e.g., Author, Publication Title, Identifiers, Abstract) Limiting search o Scroll down to see options for limiting your search (e.g. age of subject, years of publication, publication type, etc) o Click on options you want II. Choosing relevant articles from the references that your search generates Hint. If your search generates irrelevant publications or provides a large number of hits, you might consider refining your search terms. You can click on the pull-down menu at the right that says Sort Results by to change the order of records. Click on the article title to see the Abstract of an article. Read this to find out more information about the article and see if it is applicable to your research interests. Check the box that says Save to My Research to save articles you are interested in. Click on the Save to My Research link to see your list of articles You can print, e-mail, and/or save your marked results by choosing the appropriate icon on the far right of the screen. III. Getting your articles Finding articles that are available in full-text format online o Click on the Get It button and see if a PDF of the article is available Finding call numbers of journals not available online o Click on the Get It button and click on the Go button under the Print option - Find the location and call number of the journal o You can also find it by searching the title in the The CAT - Go to the PSU Library Website: http://www.libraries.psu.edu - Click on The CAT - Click on Browse Titles and More tab
9 - Type in the title of the journal or book (NOT the title of the article or chapter) - Click on the appropriate search type (i.e., title, journal title, series) IV. Other frequently used databases ProQuest PubMed: Topics related to medicine and health Google Scholar: http://scholar.google.com o Most useful for finding a specific article (e.g. from the reference section of another article) or searching for a distinct phrase o Not useful for finding a comprehensive list of all articles on a topic. It should NOT be used to do a scholarly literature search. o If used on campus, will link to Penn State: Get It through library o If not on campus, click on Scholar Preferences, and search for Penn State under Library Links. Here you can login and access articles through Penn State s library resources. V. Other general tips Don t get discouraged if you can t find anything right away. Continue to change your key words or ask for help. Don t use Google or Yahoo! Those search engines are very powerful, but they won t distinguish peer-reviewed (e.g., Child Development) from popular (e.g., USA Today) articles. Google Scholar can connect you to the articles through Penn State. If you want to be more inclusive in your search, abbreviate your keywords and put an asterisk at the end. For example, if you type in: adolescen* the search engine will pull up articles with the words adolescent, adolescents, and adolescence. If you can only find one good article, look at the references these authors cited. If you find something that looks applicable within the reference section, type the title into the Advanced Tab option in PsycInfo and read the abstract. This technique is particularly helpful when you find recently published article (if the article you find is 10 years old, then everything in its reference list will be more than 10 years old) If you find a very helpful article, you can look at other articles that include the article you found in their reference list. In your search results in PsychInfo, click on Cited by under
10 the article citation and it will show you the other articles that cite the article you found. This technique is particularly useful with slightly older articles, that have been published long enough for others to refer to them in their own papers. Start early! Conducting a literature search can be a lengthy process. Be sure to give yourself enough time to find appropriate articles and read them. 2. Sampling Key Terms Population: The group of people we are interested in understanding and who we are generalizing to Example: All Penn State students Sample: The subset of the population we study in our research project (who we are generalizing from) Example: All HDFS students who agree to fill out the survey Representativeness: How well our sample represents the population; A sample is representative if it approximates the population in relevant ways (of interest to the researcher e.g. by ethnicity, gender, age, etc.) Generalizability: The extent to which conclusions based on what has been observed can be applied to what has not been observed. We are trying to generalize from the sample to the population. Sampling: the process of creating a sample from a population There are two main types of sampling procedures: non-probability and probability Non-probability Sampling: Every member of a population does not have an equal chance of being selected into the sample Does not use random selection Probability Sampling: Every member of a population has an equal chance of being included in the sample Uses random selection Easier to generalize to the population
11 A. Experimental vs. Correlational Experimental Design: 3. Empirical Design A central goal of behavioral science is to identify causes of behaviors, Researchers use experiments to establish cause and effect associations. An experiment is a study in which the investigators create initially equivalent groups, systemically manipulate an independent variable (IV), and compare the groups to see if the IV affected the dependent variable (DV). Manipulation can involve changing the level, presence or absence, intensity, frequency, or duration of the IV. Correlational Design: Researchers examine variables that cannot or should not be manipulated in correlational studies. Researchers measure different variables to see if there is an association among them, and if so, the strength and direction of those associations. Behavior is observed as it occurs naturally. B. Cross-Sectional vs. Longitudinal Cross-Sectional: A design in which an investigator studies a number of groups differing on some characteristic (e.g., age) at the same time (i.e., measure once). In other words, researchers learn about development and aging by comparing different people of different ages at one time. Cross sectional studies tell us that there are differences between age groups, but not that these differences are due to AGING! Longitudinal: A research design in which an investigator studies the same people over time (i.e., measure more than once). This design allows us to learn about development by studying how people change over time. Longitudinal designs actually tell us about age change not age differences.
12 C, Qualitative vs. Quantitative: Qualitative Quantitative Research Question What is the experience of (a particular phenomenon)? Is there an association between X and Y? Type of Questions Open-ended, probing Closed-ended, limited probing Variables Under Study To be uncovered Pre-determined Sample Size Generally small Large Amount of Info per Participant Data Collection Type of Analysis Much; Depth; Long narratives Usually in person, interview, observation Interpretive, uncovering themes, textual Varies; Breadth Surveys, observational, questionnaires Statistical, numerical 4. Descriptive Statistics A. Frequency Distributions and Histograms Frequency distribution: An arrangement of a set of scores from lowest to highest that indicates the number of times each score was obtained. Histogram
13 B. Measures of Central Tendency Mode: the most frequently occurring value in a distribution Mean (M): the arithmetic average score of a distribution (used only with continuous variables) Median: the middle score in the distribution of scores (used only with continuous variables) C. Measures of Dispersion/Variability Range: The difference between the lowest and highest values in a distribution Standard Deviation (s or σ): The average deviation, or difference, from the mean score in a distribution 5. Inferential Statistics A. Statistical Significance and Hypothesis Testing Hypothesis testing is the use of statistics to determine the probability that a given hypothesis is true. A researcher must: 1) Develop a null and alternative (research) hypothesis. The null hypothesis (H o ) assumes that there is no difference or association between variables whereas the alternative hypothesis (H 1 ) assumes that there is a difference or association. The alternative hypothesis is what the researcher typically wants to happen. 2) Choose a statistical test to use in order to analyze the data and see if the results support or reject the null hypothesis. 3) Determine whether the probability that the findings are due to chance is below a certain level (e.g., 5%). The researcher examines the p-value provided with the statistical test. A result is statistically significant if the p-value is lower than the chosen alpha level (often p <.05*). A statistically significant result means that the results were unlikely due to chance and that the researcher can reject the null hypothesis in favor of the alternative hypothesis. * A p-value of.05 means that there are only 5 chances out of 100 that the results are due to random error.
14 Take away message: If you are reading a research article and see a p-value of <.05, then that means that there is a group difference, a significant association, or an effect of the experimental manipulation or intervention. However, just because something is statistically significant does not mean that it is important or has practical significance. For example, a decrease in one unit of aggressive behavior may be statistically significant but not practically significant. B. Statistical Tests Correlation: We use a correlation when we are interested in examining the association between two continuous variables. A correlation coefficient (r) tells us about the strength and the direction of the association (positive or negative). Correlations range from -1 to 1 with the strongest possible correlation being +/-1. A correlation of zero indicates no association. A positive correlation suggests that as one variable increases, the other variable increases as well. A negative correlation indicates that as one variable increases, the other variable decreases. H o : There is no association between X and Y H 1 : There is an association between X and Y Scatterplots T-Test: Used to examine whether two groups means are significantly different from each other t = group difference in means within-group variability Scales of measurement: o Independent/predictor variable: nominal w/ 2 levels (categorical, e.g., boy/girl; yes/no; over 60;under 60)
15 o Dependent/outcome variable: ordinal, ratio, or interval (continuous, e.g., selfesteem; weight) H o : The means of group 1 and group 2 are equal. H 1 : The means of groups 1 and 2 are not equal. Analysis of Variance (ANOVA): Allows researchers to examine differences between multiple groups (more than two; e.g., German/Italian/Swedish) o Extension of t-test Asks whether the differences among the groups are greater than the differences within the groups o F-test Scales of measurement: o Independent/predictor variable: nominal w/ more than 2 levels (categorical) o Dependent/outcome variable: ordinal, ratio, or interval (continuous) H o : There are no mean differences. H 1 : At least one group difference will be seen. Chi-Square Used when the outcome being examined is nominal and the predictor is nominal o Live/Die (common in medical research), Pass/Fail, Yes/No Compares proportions of responses within each group Can compare 2 or more groups χ 2 H o : All of the groups have equal proportions of (e.g., Republicans) H 1 : There is at least one significant group difference.
16 6. Critical Thinking Remember when you are reading research that an important task as a consumer of research is to think critically! As such, think in terms of alternative explanations for the results. In 312W, we discussed the third variable problem, internal validity, and external validity. These should all be considered when determining the validity of the findings. Third variable problem: In correlational studies, the correlation between the two primary variables may be due to an outside (third) variable which is the cause. Example: A positive correlation between ice cream consumption and number of drowning incidences may be due to a third variable of temperature. As temperature increases so does the amount of ice cream consumed and the number of drowning incidences as more people are swimming. Internal validity: the degree to which a causal association can be established between an independent (predictor) variable and dependent (outcome) variable (i.e., can third variables be ruled out as causes) Example: A researcher invites a group of students to take a memory test at 8am. They are given decaffeinated coffee. The researcher then invites a second group of students to take a memory test at noon. They are given caffeinated coffee. This study does not have internal validity because caffeine is confounded with time of day. In assessing internal validity, it is also important to look out for threats to validity such as history, selection differences, instrumentation, and attrition. External validity: the extent to which the results can be generalized to other populations and settings beyond those in the research study Example: A research study which only includes people from State College will not have strong external validity because most people in State College are college students or university employees, and there is little racial diversity. The findings from such a study may not generalize to certain races, to larger cities, or to non-university affiliated individuals.