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The Practice of Social Research

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Title: The Practice of Social Research Author: Aurea K Osgood Last modified by: T.L. Warburton Created Date: 9/11/2008 2:35:26 PM Document presentation format – PowerPoint PPT presentation

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Title: The Practice of Social Research


1
The Practice of Social Research
  • Chapter 16 Statistical Analysis

2
Chapter Outline
  • Descriptive Statistics
  • Inferential Statistics
  • Other Multivariate Techniques
  • Quick Quiz

3
Descriptive Statistics
  • Descriptive Statistics statistical computations
    describing either the characteristics of a sample
    or the relationship among variables in a sample.

4
Descriptive Statistics
  • Measures of Association
  • Proportionate Reduction of Error (PRE) a
    logical model for assessing the strength of a
    relationship by asking how much knowing values on
    one variable would reduce our errors in guessing
    values on another variable.

5
Descriptive Statistics
  • Nominal Variables
  • Lambda (?)
  • Ordinal Variables
  • Gamma (?)
  • Interval and Ratio Variables
  • Pearson (r)

6
Descriptive Statistics
  • Regression Analysis a method of data analysis
    in which the relationships among variables are
    represented in the form of an equation, called a
    regression equation.
  • Linear Regression Analysis a form of
    statistical analysis that seeks the equation for
    the straight line that best describes the
    relationship between two ratio variables.
  • Multiple Regression Analysis a form of
    statistical analysis that seeks the equation
    representing the impact of two or more
    independent variables on a single dependent
    variable.

7
Descriptive Statistics
  • Linear Regression
  • Regression Line
  • Unexplained Variation
  • Explained Variation

8
Descriptive Statistics
  • Multiple Regression
  • Partial Regression Analysis a form of
    regression analysis in which the effects of one
    or more variables are held constant, similar to
    the logic of the elaboration model.
  • Curvilinear Regression Analysis a form of
    regression analysis that allows relationships
    among variables to be expressed with curved
    geometric lines instead of straight ones.

9
Inferential Statistics
  • Inferential Statistics the body of statistical
    computations relevant to making inferences from
    findings based on sample observations to some
    larger population.

10
Independent Variable Independent Variable Independent Variable
Dependent Variable Nominal Ordinal Interval/Ratio
Dependent Variable Nominal Crosstabs Chi-Square Lambda Crosstabs Chi-Square Lambda
Dependent Variable Ordinal Crosstabs Chi-Square Lambda Crosstabs Chi-Square Lambda Gamma Kendalls tau Sommers d
Dependent Variable Interval/Ratio Means t-test ANOVA Means t-test ANOVA Correlate Pearson s Regression (R)
11
Inferential Statistics
  • Univariate Inferences
  • Cautions about Making Inferences
  • The sample must be drawn from the population
    about which inferences are being made.
  • The inferential statistics assume several things
    (a) simple random sampling, (b) sampling with
    replacement, (c) 100 percent completion rate
  • Inferential statistics are addressed to sampling
    error only, not nonsampling error.

12
Inferential Statistics
  • Tests of Statistical Significance
  • Statistical Significance a general term
    referring to the likelihood that the relationship
    observed in a sample could be attributed to
    sampling error alone.
  • Tests of Statistical Significance a class of
    statistical computations that indicate the
    likelihood that the relationship observed between
    variables in a sample can be attributed to
    sampling error alone.

13
Inferential Statistics
  • The Logic of Statistical Significance
  • Assumptions regarding the independence of two
    variables in the population study
  • Assumptions regarding the representativeness of
    samples selected through conventional
    probability-sampling procedures
  • The observed joint distribution of sample
    elements in terms of the two variables

14
Inferential Statistics
  • Level of Significance in the context of tests
    of statistical significance, the degree of
    likelihood that an observed, empirical
    relationship could be attributed to sampling
    error.
  • A relationship is significant at the .05 level if
    the likelihood of its being only a function of
    sampling error is no greater than 5 out of 100.

15
Inferential Statistics
  • Chi-Square
  • Based on the null hypothesis.
  • Computation
  • For each cell in the table, subtract the expected
    frequency for that cell from the observed
    frequency.
  • Square the quantity.
  • Divide the squared difference by the expected
    frequency.
  • Chi-Square Table

16
Inferential Statistics
  • t-Test
  • Measure for judging the statistical significance
    of differences in group means.
  • Logic
  • The value of t will increase with the size of the
    differences between means.
  • The value of t will also increase with the size
    of the sample involved.
  • The value of t will be larger when variations of
    values within each group are smaller.

17
Inferential Statistics
  • Caution
  • There are no objective tests of substantive
    significance (only objective significance).
  • Statistical significance is only appropriate for
    samples, and not for whole populations.
  • Tests of significance are based on the same
    sampling assumptions used to compute confidence
    intervals.

18
Other Multivariate Techniques
  • Path Analysis a form of multivariate analysis
    in which the causal relationship among variables
    are presented in a graphic format.

19
Other Multivariate Techniques
  • Time-Series Analysis an analysis of changes in
    a variable over time.

20
Other Multivariate Techniques
  • Factor Analysis a complex algebraic method for
    determining the general dimensions of factors
    that exist within a set of concrete observations.

21
Other Multivariate Techniques
  • Analysis of Variance (ANOVA) method of analysis
    in which cases under study are combined into
    groups representing an independent variable, and
    the extent to which the groups diff from one
    another is analyzed in terms of some dependent
    variable. Then, the extent to which the groups
    differ is compared with the standard of random
    distribution.

22
Other Multivariate Techniques
  • Discriminant Analysis method of analysis
    similar to multiple regression, except that the
    dependent variable can be nominal.

23
Other Multivariate Techniques
  • Log-Linear Models data analysis technique based
    on specifying models that describe the
    interrelationships among variables and then
    comparing expected and observed table-cell
    frequencies.

24
Other Multivariate Techniques
  • Geographic Information Systems (GIS) analytic
    technique in which researchers map quantitative
    data that describe geographic units for a graphic
    display.

25
Quick Quiz
26
Chapter 16 Quiz
  • 1. _____ indicate the likelihood that the
    relationship observed between variables in a
    sample can be attributed to sampling error only.
  • Ex post facto hypothesizing
  • Tests of statistical significance
  • Disconfirmation

27
Chapter 16 Quiz
  • ANSWER B.
  • Tests of statistical significance indicate the
    likelihood that the relationship observed between
    variables in a sample can be attributed to
    sampling error only.

28
Chapter 16 Quiz
  • 2. _____ is a causal model for understanding
    relationships between variables.
  • Ex post facto hypothesizing
  • Tests of statistical significance
  • Disconfirmation
  • Path analysis

29
Chapter 16 Quiz
  • ANSWER D.
  • Path analysis is a causal model for understanding
    relationships between variables

30
Chapter 16 Quiz
  • 3. _____ are statistical measures used for making
    inferences from findings based on sample
    observations to a larger population.
  • Descriptive statistics
  • Inferential statistics
  • both of the above
  • none of the above

31
Chapter 16 Quiz
  • ANSWER B.
  • Inferential statistic are statistical measures
    used for making inferences from findings based on
    sample observations to a larger population.

32
Chapter 16 Quiz
  • 4. A _____ analysis represents changes in a
    variable over time.
  • regression
  • bivariate
  • time-series
  • log-linear

33
Chapter 16 Quiz
  • ANSWER C.
  • A time-series analysis represents changes in a
    variable over time.
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