Introduction to Statistics.pdf

Overview 1 Introduction to Psychological Statistics PSY112 – Lecture and Laboratory PSY112: Psychological Statistics  Overview...

Overview 1 Introduction to Psychological Statistics PSY112 – Lecture and Laboratory PSY112: Psychological Statistics  Overview 1 WHAT’S IN IT FOR ME? Statistics will help me contribute to the objectives of Psychology. Statistics is crucial to being able to read psychology research articles and doing research yourself. Statistics develops my analytic and critical thinking. PSY112: Psychological Statistics  Overview 1 HOW WILL I DO IT? Read, read and read. Give your 101% attention to the discussion. Do not move on to the next concept without understanding the previous one. Always put an effort to catch up whenever there are absences. Ask me questions and clarification. Help each other. PSY112: Psychological Statistics  Overview 1 WHAT IS PSYCHOLOGY? Scientific study of human behavior and mental processes to HELP UPLIFT THE HUMAN CONDITION. More specifically, to Describe, Predict, Explain and Control behavior. PSY112: Psychological Statistics  Overview 1 DESCRIPTION - Refers to a systematic and unbiased account of the observed characteristics of behaviors. PREDICTION - Refers to the capacity for knowing in advance when certain behaviors would be expected to occur—to be able to predict them ahead of time—because we have identified other conditions with which the behaviors are linked or associated EXPLANATION - includes knowledge of the conditions that reliably reproduce the occurrence of a behavior. CONTROL - Refers to the application of what has been learned about behavior. Once a behavior has been explained through experimentation, it may be possible to use that knowledge to effect change or improve behavior. PSY112: Psychological Statistics  Definition of Statistics 1 WHAT IS STATISTICS? Statistics is an art of learning from the data. It is a branch of knowledge which deals with collection, presentation, analysis and interpretation of data. According to W.A. Wallis, it maybe defined as a body of methods for making wise decisions in the face of uncertainty. PSY112: Psychological Statistics  Definition of Statistics 1 Consider an Example Psychologists have long been interested in the relationship between stress and health. A focused question might involve the study of a specific psychological symptom and its impact on the health of the population. To assess whether the symptom is a good indicator of stress we need to measure the symptom and stress levels in a sample of individual from the population. It is not immediately clear how we should go about collecting this sample, i.e. how we should design the study. We haven’t got very far before we need Statistics! PSY112: Psychological Statistics  Definition of Statistics 1 ROLE OF STATISTICS IN SCIENTIFIC PROCESS PSY112: Psychological Statistics  Basic Statistical Terms 1 BASIC STATISTICAL TERMS Population is the set of all individuals or entities under consideration or study. Study: Suppose that a researcher is interested in the stress level of basic education teachers during the preparation for online classes. Parameter is a value – usually numerical - that describes a population Example: All basic education teachers are college graduates. PSY112: Psychological Statistics  Basic Statistical Terms 1 Sample is a set of individual selected from a population, usually intended to represent the population in a research study. Statistic is a value usually a numerical value that described the sample. PSY112: Psychological Statistics  Basic Statistical Terms 1 Relationship between Sample and Population PSY112: Psychological Statistics  Basic Statistical Terms 1 Variable A characteristic or attribute of persons or objects which assumes different values or label. This is a thing that we measure, control or manipulate in a research varying from unit to unit. Example: Suppose we collect a dataset by measuring the resting heart rate, score of an IQ test, favorite color of every student in a class. The variables in this dataset would be resting heart rate, score of an IQ test, favorite color. PSY112: Psychological Statistics  Basic Statistical Terms 1 Values is a possible number of category that a score can have Example: 0-20 in a Depression Scale, Male or Female Score or Raw Score is a particular person’s value on a variable. Data (plural) a measurements or observation. Datum (singular) – a single measurement or observation and is commonly called a score of raw sore. Data Set A collection of measurements or observation PSY112: Psychological Statistics  Basic Statistical Terms 1 Some of the statistical measures and symbols are presented in the table. (Parameters are denoted by Greek letters to honor the contribution of ancient Greek philosophers. - Sir Ronald A. Fisher, father of modern day Statistics.) PSY112: Psychological Statistics  Basic Statistical Terms 1 Learning Check A researcher is interested in the effect of amount of sleep on high school students’ exam score. A group of 75 high school boys agree to participate in the study. The boys are.. A nutritionist is interested in studying the effect of a new diet plan on weight loss among adults. She wants to know whether this diet is effective in reducing weight over a 6-month period. To conduct the study, she selects a group of 150 adults from a large city who are willing to follow the diet plan and tracks their weight loss. A company wants to assess the overall job satisfaction level of its employees to identify areas for improvement. The HR department conducts a survey using a standardized job satisfaction questionnaire. PSY112: Psychological Statistics  Nature of Statistics 1 AIMS OF STATISTICS Statistics aims to uncover structure in data, to explain variation Descriptive Inferential PSY112: Psychological Statistics  Nature of Statistics 1 Descriptive Statistics It pertains to the methods dealing with the collection, summarization, organization, simplification and analysis of a set of data without making conclusions, predictions or inferences about a larger set. PSY112: Psychological Statistics  Nature of Statistics 1 Example Presentation of the Trend of Mortality from Suicide and Self-inflicted Injuries in the Philippines from 1980-2000. Last year, 80% of the employees of a company were absent for at least 10 working days. All students took the midterm exam on time. PSY112: Psychological Statistics  Nature of Statistics 1 Inferential Statistics This pertains to the methods dealing with making inferences, estimation or prediction about a larger set of data (population) using the information gathered from a subset of this larger set (sample). Consists of techniques that allow us to study sample and then make generalizations about the populations from which they were selected. PSY112: Psychological Statistics  Nature of Statistics 1 Example The time required by a robot to do a repetitive task is determined by a few sample observation. 80% of the public jeepney drivers are at considered high risk of having health problems. Regular exercisers are 70% less likely to develop heart disease compared to those with a sedentary lifestyle. 75% of long-term smokers are at a significantly higher risk of developing lung cancer compared to non-smokers. PSY112: Psychological Statistics  Nature of Statistics 1 TYPE OF DATA Qualitative Data (Categorical) Occur when we assign objects into labelled groups or categories. Example - when we group people according to Marital Status, Socio-Economic Status, Religious Sector, zip code, and military rank PSY112: Psychological Statistics  Nature of Statistics 1 TYPE OF DATA Quantitative Data Occur when we count or measure. Example - count the number of students in a classroom, measure the weight and height of a respondent, and count the monthly income of managers in pesos Discrete Variable – consists of separate, indivisible categories (number of students, number of correct answers) Continuous Variable – there are an infinite number of possible values that fall between any two observed values. Ex. Speed, height, weight, temperature PSY112: Psychological Statistics  Nature of Statistics 1 LEVELS OF MEASUREMENT Nominal Scale Does not indicate an amount, rather, it is used for identification, as a name. Variables with values that are categories, also known as categorical variables. Examples: gender, race, color, and savings account number, nationality, religion PSY112: Psychological Statistics  DefinitionNature of Statistics 1 of Statistics LEVELS OF MEASUREMENT Ordinal Scale Indicates rank order. There is no equal unit of measurement separating each score. Also known as rank-order variable Examples: socioeconomic status of families, Class Standing (A to D), and Teacher’s Evaluation (Excellent to Poor), Self-Confidence ( Low, Average, High), Likert Scale PSY112: Psychological Statistics  Nature of Statistics 1 Interval scale Indicates an actual quantity and there is an equal interval between numbers. Interval scales do not have a ”true” 0 or absolute zero point. Examples: temperature, IQ, Stress PSY112: Psychological Statistics  Nature of Statistics 1 Ratio Scale Reflects the true amount of the variable that is present because the scores measure an actual amount, there is an equal interval between numbers, and 0 truly means that zero amount of the variable is present. Examples: time, height, weight, width, area, and income. PSY112: Psychological Statistics  Nature of Statistics 1 Quantitative Quantitative Qualitative Qualitative PSY112: Psychological Statistics  Nature of Statistics 1 Important to Note: Most psychological variables (eg. intelligence, aptitude, personality) strictly speaking are ordinal. However, most psychologist treat those data as interval because they are much flexible for statistical manipulation/analysis PSY112: Psychological Statistics  Nature of Statistics 1 Learning Check Indicate whether the following statements require the use of descriptive or inferential statistics: The Socio-Economic Status of the family is related to the educational level of the household head. Amongst the subject areas, Science was the least of the competencies of both elementary and secondary students at 54.1% and 39.5 %, respectively, according to DepEd. Girls learn to speak at an earlier age than boys. PSY112: Psychological Statistics  Nature of Statistics 1 Learning Check Identify the following as qualitative or quantitative variable. If quantitative, classify whether discrete or continuous. Also, indicate the level of measurement required in each. Annual Income of employees in pesos. Citizenship Birth order in family Adversity Quotient of College graduating students. Time Level of Satisfaction Birth Year PSY112: Psychological Statistics