PSY 2400 - Week 1
PSY 2400 - Week 1 Psy 2400
Popular in Statistical Methods
Popular in Psychology (PSYC)
This 7 page Class Notes was uploaded by Natalie on Sunday September 4, 2016. The Class Notes belongs to Psy 2400 at Texas Tech University taught by Amelia Littlefield in Fall 2016. Since its upload, it has received 90 views. For similar materials see Statistical Methods in Psychology (PSYC) at Texas Tech University.
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Date Created: 09/04/16
PSY 2400 – Statistical Methods 09/01/2016 ▯ Chapter Concepts 2 branches of statistical methods basic concepts kinds of variables ▯ Learning Outcomes Key statistical terms Key measurement terms Key research terms Know the place of statistics in science Understand summation notation ▯ Asses the situation Statistics requires basic math skills Inadequate basic math skills puts you at a disadvantage in this course Appendix A math skills assessment helps you determine if you need a skills review ▯ Statistics, science and meaningful observation Statistics = statistical procedures Statistics are used to o Organize and summarize information o Determine what conclusions are justified based on the date Goals of statistical procedures o Accurate and meaningful interpretation o Provide standardized ways to address testable hypotheses ▯ Why learn statistics? It’s required to graduate Increase your understanding of media graphics and research articles So you can learn how to do your own research, be the master of your own destiny Can improve your critical reasoning and intuitive understanding of how the world works ▯ Populations vs. Samples Population o The set of ALL the individuals of interest in a particular study (who do you expect the conclusions apply to?) o Vary in size; often quite large o Entire set of things of interest E.g. the entire piggy bank of coins E.g. the entire population of individuals in the US Sample o A subset of individuals selected from a larger population (who are you using to answer your research question?) o Usually intended to represent the population in a research study o The subset of the population about which you actually have information E.g. a handful of coins E.g. 100 men and women who answered an online questionnaire about health care usage Population symbols are GREEK to you, literally: o Mean = μ = Mu (pronounced “Mew”) o Standard deviation = σ = Sigma o Variance = σ2 = Sigmasquared Sample Symbols are more familiar o Mean = M = X o Standard deviation = SD = s o Variance = SD2 = s2 ▯ Why use samples instead of populations? More practical and costeffective to obtain information from a sample than a population The goal of research is to make predictions about entire populations Social and behavioral research is conducted by evaluating a sample of individuals who are believed to be “representative” of a population of interest ▯ Speaking statistically: variables and date Variable o Characteristic or condition that changes or varies among different individuals in your sample Date set o A collection of measurements or observations Data (plural noun) o Measurements or observations of a variable Datum (singular noun) o A single measurement or observations o Commonly called a score or raw score Variable = characteristic or condition that can have different values o E.g. level of stress; time of day; number of freckles Value = any possible number or category a score can have o E.g. 010 Score = particular person’s variable value o E.g. a study participant rates her current level of stress as a 5 on a scale of 010 Methods of Sampling Random selection o Choosing a sample so that every individual in the population has an equal chance of being selected E.g. using a random number table Haphazard (or “convenience”) selection o Selecting a sample of individuals to study based on whomever is available or happens to be around This method can result in a sample that is not representative of a population ▯ Parameters and Statistics Parameter o Value, usually a number, that describes a feature of the population o derived from measurements of the individuals in the population Statistic o A value, usually a number, that describes a feature of the sample o Derived from measurements of the individuals in a given sample ▯ Soooo – what is statistics? A branch of mathematics that focusses on the organization, analysis, and interpretation of a set of numbers Wo main branches of statistics o Descriptive statistics Summarize and describe date from a sample o Inferential statistics Draw conclusions based on sample data that you expect will apply/generalize to the population of interest ▯ Descriptive & Inferential Statistics Descriptive statistics o Summarize o Organize o Simplify o Ex: Tables Graphs Averages Percentages Inferential statistics o Used to make generalizations about the population o Interpret observed date o Common terminology “margin of error” “statistically significant” ▯ Sampling Error Fact: a sample is NEVER going to be identical to the populations Sampling error is the difference, or amount of error, between a sample statistic and the corresponding population parameter Example: “margin of Error” in Voting Polls o “this poll was taken from a sample of registered voters and has a margin of error of plusorminus 4 percentage points” ▯ Data structures, research methods, and statistics Variables are observed or measured o “statistics’ describe the measured variable o there are categorical and numerical variables relationships between variables o two variables are observed and measured o two ways used to determine whether a relationship exists between two variable ▯ Relationships between variables Correlational method (first way) o Only one group of participants o Two variables are measured for each participant o Goal is to describe direction (positive, negative) and strength of the relationship o Patterns in the data reveal relations among variables o Nonexperimental method ▯ ▯ Limitations of correlational method Can demonstrate the existence of a relationship But does not provide an explanation for the relationship – “cannot answer WHY?!” Most importantly, does not demonstrate a causeandeffect relationship between the two variables ▯ Relationships between variables Methods comparing groups of scores (second way) o One variable defines the groups o Scores are measured on a second variable o Both experimental and nonexperimental studies rely on this structure ▯ Experimental Method essentials Goal of experiments is to demonstrate a causeandeffect relationship The level of one variable is manipulated by the experimenter and determined by random assignment Control rules out influence of other variables o Individual difference variables o Environmental variables
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