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 1 answerLast reply by: Professor Charles SchallhornMon Nov 10, 2014 4:19 PMPost by Raquel Roman on August 10, 2014is statistics methods the same as clinical methods? 1 answerLast reply by: Professor Charles SchallhornMon Nov 10, 2014 4:27 PMPost by Avi Sabath on March 4, 2014Hi Professor Schallhorn,About how many questions are there (usually) on the AP exam directly about Standard Deviation? About how many will be related but not necessarily asking for specific numbers?Thank you very much,Avi

### Research Methods: Statistics

• Descriptive Statistics summarizes numbers so they become more meaningful and easier to communicate to other people
• Inferential Statistics are used for making decisions, for generalizing from small samples, and for drawing conclusions
• Number Scales include nominal, ordinal, interval, and ratio
• Numbers can be graphically represented by frequency distributions, histograms, and frequency polygons
• Measures of central tendency are mean, median and mode
• Measures of Variability include variability, range and standard deviation
• Standard Deviation illustrates how compressed or spread out a set of scores are
• The normal curve is used to visualize variability
• Inferential Statistics are used to determine whether or not findings can be applied to the larger population from which the sample was selected
• Statistical Significance: Degree to which an event is unlikely to have occurred by chance alone—this is called the p-value
• Most psychological research will be at the .05 level
• Intro 0:00
• Objectives 0:22
• Distinguish the Purposes of Descriptive Statistics and Inferential Statistics
• Apply Basic Descriptive Statistical Concepts, Including Interpreting and Constructing Graphs, and Calculating Simple Descriptive Statistics (e.g. Measures of Central Tendency, Standard Deviation)
• Types of Statistics 0:50
• Descriptive Statistics: Summarize Numbers So They Become More Meaningful and Easier to Communicate To Other People
• Inferential Statistics: Used For Making Decisions, For Generalizing From Small Samples, and For Drawing Conclusions
• Number Scales -- Nominal 1:30
• No Quantitative Properties
• For Comparison Only -- Grouping Participants
• E.g. a Likert Scale (e.g. On a Scale From 1-5) on Strongly Agree, Agree, Neutral, Disagree, Strongly Disagree Scale
• Number Scales 2:34
• Ordinal Scales
• Determining Ranking
• E.g. Seeds in NCAA Basketball Tournament
• The Differences Between Seeds Has No Information Beyond the Ranking
• Differences Between Rankings Not Equal -- Difference Between #1 and #4 Is Not The Same As Between #5 and #8
• #1 Seed is NOT 4 Times Better Than #4 Seed
• Number Scales -- Interval 3:14
• Lots of Data and Can Add/Subtract
• Classic e.g. is Temperature
• SAT or ACT Scores
• IQ Scores, Myers-Briggs, and Others Operate Under the Assumption of an Interval Scale
• Do NOT Have a True Zero Point
• Number Scale -- Ratio 3:55
• Contain the Most Amount of Quantitative Information
• Have a True Zero Point
• E.g. Speed, Time, Weight, Distance
• Can Meaningfully Describe Something as Twice as Fast or Four Times as Long
• Graphical Representations 4:55
• Presenting Numbers Pictorially (Usually in a Graph) So They Are Easier to Visualize
• Frequency Distribution: Table That Divides an Entire Range of Scores Into a Series of Equal Classes and Then Records The Number of Scores That Fall Into Each Class
• Histogram: Graph of a Frequency Distribution; Scores Are Represented By Vertical Bars
• Frequency Polygon: Graph of a Frequency Distribution Where The Number of Scores In Each Class Is Represented By Points on a Line
• Frequency Distribution 7:16
• Graphic
• Frequency Histogram 7:59
• Graphic
• Frequency Polygon 8:41
• Graphic
• Descriptive Statistics 9:17
• Describing Data
• Measures of Central Tendency
• Mean 9:41
• Mean (Arithmetic Average)
• Mean: Add All the Scores For Each Group and Then Divide By the Total Number of Scores; One Type of Average
• Median 11:57
• Median (Middle Score)
• Median: Arrange Scores From Highest to Lowest and Then Select The Score That Falls in The Middle; Half the Values Fall Above the Median, And Half Fall Below It
• Mode 13:18
• Mode (Occurs the Most)
• Mode: Identifies the Most Frequently Occurring Score in a Group
• A Number That Describes a Typical Score Around Which the Other Scores Fall
• Measures of Variability 13:50
• Variability -- How Spread Out or Compressed a Set of Scores Are -- Level of Dispersion
• Range -- Of a Set of Data, The Range is the Difference Between the High and Low Values
• Standard Deviation -- Represented by the Symbol σ
• Measures of Variability 14:56
• Normal Curve (Bell Shaped)
• How Do We Visualize the Variability With a Normal Curve?
• Deviations and Percentages -- Need to Become Familiar With Them
• Z-Score: Indicates How Many Standard Deviations Above or Below The Mean a Score Is
• Normal Curve: Bell Shaped Curve, With a Large Number of Scores in the Middle, and Very Few Extremely High and Low Scores
• Normal and Skewed Curves 16:13
• Examples of Negatively Skewed, Normal, and Positively Skewed Curves
• Standard Deviation 17:50
• Graphic of Bell Curve Displaying How To Measure Standard Deviations
• Normal Curve 20:45
• Graphic Showing Different Measurements of Ranges That Can Be Used With a Normal Curve
• IQ Scores and S.D. 22:36
• Always Assume That the Mean/Median/Mode is 100 for an IQ Score -- and That It's a Normal Curve
• So if x̅ (the mean) is 100, the S.D. is 15, What is John's IQ if he is 2 S.D.s Above The Mean?
• Lots of Questions Like This on the AP Exam
• Examples of Standard Deviation Problems 24:56
• What if the Mean is Not 100?
• E.g. Mean is 85 and the S.D. is 6
• E.g. Mean is 45 and the S.D. is 3
• Inferential Statistics 28:38
• Purpose is to Determine Whether or Not Findings Can Be Applied to the Larger Population From Which the Sample Was Selected
• Infer versus Imply (Joey on Friends)
• Why Might There Be Differences Between Two Groups in an Experiment?
• Inferential Statistics 30:30
• Population: Entire Set of Subjects, Objects, or Events of Interest (All Married Students in the United States)
• Samples: Smaller Cross Section of a Population
• Inferential Statistics 31:51
• Sample Must Be Representative
• Members of Sample Must Be Chosen Randomly
• Statistical Significance: Degree to Which an Event (Results of an Experiment, Results of a Drug Trial) is Unlikely to Have Occurred By Chance Alone
• Many Statistical Tests to Measure Magnitude of Difference --> T-Tests, Chi Square, and ANOVAs
• AP Psych--- Need Only to Know -- P-Value
• P-Value 33:13
• The Smaller the P-Value, The More Significant the Results
• In Science, a P-Value of .05 is Cutoff for Statistical Significance
• A P-Value of .05 Means That a Five Percent Chance Exists That the Results Occurred By Chance
• A P-Value of .01 Means That a One Percent Chance Exists That the Results Occurred By Chance
• Most Psychological Research Will Be at the .05 Level
• Review Questions 34:12
• What is the Best Way to Choose Subjects?
• Distinguish Between Descriptive and Inferential Stats
• Distinguish Among Mean, Median and Mode
• What is the Purpose of the Standard Deviation
• How Does Random Selection Increase the Importance of the Results of a Study?