PSYC200 EXAM 1Statistics- numerical value that represents a sample (partial data); 2 branches- Descriptive Statistics - used to summarize, organize, and present data in a convenient and communicable form o (Ex: summarize exam scores by reporting class avg)- Inferential Statistics - techniques that allow us to make inferences or conclusions about a population based on data that are gathered from a sample∑xy multiply x and y values then add them all up∑x∑y sum of x values * sum of y values∑(x+1) add 1 to each x value and then sum them all∑x+1 add 1 to the sum of all of the x values∑x^2 square all of the x values then sum themData- collection of measurements or observations made on subjectsPopulation- collection of all people, objects, events, observations sharing one or more specified characteristics- Parameter- value that describes a characteristic of a populationSample- subset of individuals selected from a population, intended to reflect the population in a studyo Statistic- value that describes a characteristic of a sample- Convenience Sampling - selecting individuals for a sample that are easily accessible; often biasedo Biased sample- under/over-represents parts of the population- Random Sample- every possible sample size “n” has same chance of being selected; unbiased b/c no part of the population has advantage of being over-represented- Sampling Errorso Random sampling error- random sample may not be due to chance aloneo Non-random sampling error- arise from improper sampling (nothing to do with chance) - Non-sampling errors- errors not related to selecting the sample (for convenience sampling)o Missing data, response errors, processing errorsExperiments- researcher creates and controls groups; able to manipulate a variable- Variable - free to vary; can take on at least one other value (ex: height, IQ, GPA, hair color)o Independent- examined to determine its effects on an outcome of interest; often manipulated; consists of at least 2 levels/categorieso Dependent- outcome of interest that is being observed and measured in order to assess effects of independent variablePSYC200 EXAM 1- Constant - characteristic that does not change its value in a given context (ex: days in a week, sample size)Non-experimental studies- used when we cannot manipulate everything- Naturalistic observation - participants not aware they are being observed- Parameter estimation - how much of something occurs; averages; percent’s; uses whole populations- Correlational studies - how two variables relate; participant provides something quantitative (measurable)o Predictor variable - like the independent, but is often measured rather than manipulated, not always but generally is continuouso Criterion variable - (like the dependent)- outcome of interest that is observed and measured in order to assess the effects of the predictor variable; the actual observations or measurements that are recordedDiscrete Variable- consists of separate, indivisible categories; finite # between 2 points (no values btw the categories); categorical or qualitative variablesEx: gender, religion, # of siblingsContinuous Variable- infinite # of possible values that fall btw 2 points; numerical orquantitative variablesEx: family income, test scores, eight, ageMeasurement- process of assigning numbers to objects or events according to a set of rules; 4 levels- Nominal - classify observations into categories- Ordinal - observations are rank ordered in terms of size/magnitude; does not tell how much difference there is between groups- Interval - quantitative scale that requires a constant unit of measurement; intervals between #s are equal in size; no true 0-point (0 doesn’t mean absence of that quality)- Ratio - similar to interval, but there is a 0-point (0 is the absence of a quality); cannot have a negative valueResearch Question- can’t be causalEx: Is increased tangoing positively/negatively related to cortisol levels?Theory- general idea of how concepts relate/interact; can be causalEx: Increased tangoing causes decrease in stress levelsHypothesis- specific prediction about current study/experiment; uses concrete measured variables; cannot be causal in a correlational study (but can be in an experiment)Ex: As the # of hours spend tangoing increased, your cortisol levels decrease.PSYC200 EXAM 1Frequency Distribution – organization of data indicating the number of people that obtained a certain score or fell in a certain category (table or graph)- Frequency = count of observations with the same value (sum = N)- Relative Freq = f / N (sum of all rel f’s = 1)- Cumulative Freq (cum f)– the number of people/scores who are in or below each class interval (last value = # of subjects you have (N))- Cumulative Relative Freq (Cum rel f)= (Cum f)/N the relative frequency of people/scores who are in or below each class interval (last value = 1)- Percentile = (100(cum f))/N (last value in the column = 100)Grouped Frequency Distribution- Interval width= range/# of intervalso Range= Xgreatest-Xleast- Make apparent limitso Lowest apparent limit must be divisible by interval width- Find real limits- Midpoints (used on x axis of bar graphs, histograms, frequency polygons)o ½(Upper interval value + lower interval value)- Count scores in each interval - Sum counts into frequencies Rel f, Cum f, Cum Rel f, percentilesReal Limits- reflect continuous nature of variables; midway between scores- Apparent limits - original intervals- Lowest Level Measurement- smallest possible difference between any two scoreso N= (Smallest unit of measurement / 2)o Upper Real Limit : Score + No Lower Real Limit : Score – NGraphing- Bar graph - nominal or ordinal data (only use for categories); bars don’t touch- Histogram- ratio or interval data; bars touch to encompass all scores- Frequency Polygon- interval or ratio data- Stem and Leaf Plot Central Tendency- measure that identifies a score that best represents the group- Mean (problematic with extreme scores); always closest to skew (tail)- Median (used for skewed data)- Mode (tallest bar or point on a graph); ONLY measure that can be used for nominal datao Unimodalo Bimodalo MultimodalPSYC200 EXAM 1- Shape of Curveso Symmetry: mean = mediano Modality- how many modes; where are they?o Skewness: mean ≠ median; (skewness is fewness tail=less) Right Skew- Positive, mode is
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