Welcome Back Learning Objectives: 1. Identify variables in research 2. Describe Relationships btwn 3. Explain why samples used to describe population 4. Explain random sampling and representative samples 5. Distinguish btwn Descriptive & Inferential Stats 6. Distinguish btwn experimental & correlational study 7. Identify & distinguish scales of measurement

Research Process Interest in something –“Playing video games leads to violence” –Goal: Discover LAWS OF NATURE “Somethings” are called Variables Variables –Independent variables- the “thing” that influences the behavior –Dependent variables- the outcome or result of the independent variable

Examples of Variables Independent –Vegetables –Vitamins –Drugs –Smiling –Examples? Dependent –Cancer –Immune System –Alzheimers –Helping or Altruism –Examples?

Relationship between Variables Relationship: occurs when a chg in one var. is accompanied by a consistent chg. in another var. Strength: Degree of chg in X is associated with chg in Y Types of relationships: –Increase, increase –Increase, decrease –Decrease, decrease –Zero

Populations & Samples Population-all members of group Parameters-numbers that describe Sample-subset of pop designed to be representative Statistic-numbers that describe Every student at BC Students in a History class at BC

pling_dist/ pling_dist/Why? –Cheaper –Practical –Representative

What is “done” to samples? Describe –Use descriptive statistics to organize & summarize characteristics of data Example: The average test score was 87% Infer –Use inferential statistics to decide whether sample data represents a particular relationship in population Example: Reading the textbook significantly increased test scores.

Characteristics of a Study Question about characteristic of sample or pop is asked Design study to answer question –Who-How many -When-What Conduct study –Correlational –Experimental

Correlational Study Goal: To determine if relationship btwn two or more var is present No variables are manipulated or made to occur, they are simply measured As such  cannot infer causality –Can’t say X causes Y –Only X and Y are related

Example Researcher’s Question: -Is there a relationship btwn ice cream sales and crime rate? Design of study: measure sales & crime rates Yes, a positive, strong relationship is present –Doesn’t mean ice cream causes crime Ice Cream Sales Temperature

Experimental Study Goal: To determine if relationship (causality) exists btwn variables Variable (indep) are manipulated or changed to see chg in beh (dep var) Can *infer causality –X causes chg in Y *Caution: causal statement based on probability –Never says PROVES –Other variables could be responsible for change in dependent variable

Example Researcher’s Question: -Does ice cream cause or have an effect on criminal behavior Design of study: P’s in diff conditions of ice cream (levels of indep var) and measure criminal beh (dep var) Yes, a probable causal relationship is present –P’s that ate 1 or 2 scoops of ice cream committed more crimes –PROBABILITY 012 Scoops of Ice Cream Number of Crimes Committed

Type of Data or Characteristics of Scores Type of data or dependent var you’re interested in will determine what statistic you can use –Numbers you record have diff mathematical characteristics Characteristics of numbers –Levels of measurement –Continuous or discrete

Scales of Measurement Nominal Scale: scores used for identification or naming. Ex: categories Ordinal Scale: scores indicate rank or ordering. Ex: relative amount Interval Scale: scores indicate actual amount. Ex: numbers –**0 doesn’t necessarily mean non Ratio Scale: scores indicate actual amount Ex: numbers (0 actually means none)

Continuous or Discrete Continuous: allows fractional amounts (continues btwn whole numbers) –Usually Scale (ratio & interval) Test score 97.6 IQ score Discrete: measures only whole numbers –Usually Nominal or Ordinal Male or Female Eye color –Can be Scale Ice cream or no ice cream No. of crimes 3

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Questions? Let’s get Active with a CLE Homework: Finish Ch.1 & 2 study guid –Review notes & text –Finish Ch. 1 & 2 of study guide –Preview Ch. 3 Bring –Questions, book, calculator, pencils Be ready for quiz