Data analysis method technique

1. Power Point Slides by Ronald J. Shope in collaboration with John W. Creswell
Chapter 7
Analyzing and Interpreting Quantitative Data

2. Educational Research 2e: Creswell
Steps in quantitative analysis and
interpretation
• How do you prepare the data for analysis?
• How do you analyze the data?
• How do you report the results?
• How do you discuss the results?

3. Educational Research 2e: Creswell
How do you prepare the data
for analysis? Inputting data
• Score data by assigning numeric codes
to responses
• Create codebook
• Use information from instrument when
possible as part of coding scheme
• Create data file in data grid
• Create variable, value labels
• Clean database, missing values

4. Educational Research 2e: Creswell
Determine types of Scores to
analyze
• Single item
• Summed scores
• Difference scores

5. Educational Research 2e: Creswell
Selecting a statistical
program
• Statistical Package for Social Sciences
(SPSS) most popular
• Other programs
– Mini-tab
– Statview
– SAS (JMP/JMPIN)
– StatPac
• Use mainframe, PC or Mac platforms

6. Educational Research 2e: Creswell
How do you analyze the data?
Conduct descriptive analysis
• Conduct descriptive analysis
– Measures of central tendency
– Measures of variability
– Measures of relative standing

7. Educational Research 2e: Creswell
Run Descriptive statistics
Descriptive Statistics
Central Tendency Variability Relative Standing
Mean
Median
Mode
Variance
Standard Deviation
Range
Z-Score
Percentile Ranks

8. Educational Research 2e: Creswell
Conduct inferential analysis
• Hypothesis testing
• Confidence interval
• Effect size

9. Educational Research 2e: Creswell
Conduct hypothesis tests
• Identify a null and alternative hypothesis
• Set the level of significance (alpha level)
for rejecting the null hypothesis
• collect data
• Compute the sample statistic
• Make a decision about rejecting/failing
to reject

10. Educational Research 2e: Creswell
Computing the sample statistic
Inferential Statistics
Parametric
Nonparametric
Parametric
Nonparametric Nonparametric
Parametric Chi-Square
Analysis
Phi
Coefficient
Pearson
Correlation
Coefficient
Regression
Coefficient
Spearman
Rho
Kendall’s
Tau
Continuous (iv)
Continuous (dv)
Continuous (iv)-
Continuous (dv)
Continuous (iv)-
Continuous (dv)
Continuous (iv)-
Continuous (dv)
T-Test
Analysis
of
Variance
Analysis
of
Covariance
Mann-
Witney
U-Test
Kruskall
Wallis
Test
Friedman
Two-Way
Anova
Discriminant
Analysis
Point
Biserian
Correlation

11. Educational Research 2e: Creswell
How to select an appropriate
statistic (see Table 7.5)
• Determine the type of quantitative research
question or hypothesis you want to analyze
• Identify the number of independent variables
• Identify the number of dependent variables
• Identify whether covariates and the number of
covariates are used in the research question
or hypothesis

12. Educational Research 2e: Creswell
How to select an appropriate
statistic (see Table 7.5)
• Consider the scale of measurement for
your independent variable(s) in the
research question or hypothesis
• Identify the scale of measurement for
the dependent variables (e.g.
continuous or categorical)
• Determine if the distribution of the
scores is normal or skewed

13. Educational Research 2e: Creswell
Normal Curve
34%
34%
13.5%
13.5%
2.5% 2.5%
Standard Deviations
Mean +1 +2 +3
-1
-2
-3

14. Educational Research 2e: Creswell
The Normal Curve of Means Differences of
All Possible Outcomes if the Null Hypothesis
is True
Reject the
Null
Hypothesis
Reject the
Null
Hypothesis
Extremely low
Probability Values
if Null Hypothesis
is True (Critical
Region)
Alpha=.025 Extremely low
Probability Values
if Null Hypothesis
is True (Critical
Region)
Alpha=.025
Two-Tailed Test
High Probability
Values if the Null
Hypothesis is True

15. Educational Research 2e: Creswell
Outcomes of hypothesis testing:
Type I and type II errors
State of Affairs in the Population
Decision made by
the Researcher
Based on the
Statistical Test
Value
Type I Error
(false positive)
(probability=
Alpha)
Correctly not
rejected
no error
Correctly
rejected
no error
(probability=
power)
Type II Error
(false negative)
(probability=
Beta)
Reject the
Null
Hypothesis
No Effect-
Null True
Effect Exists
Null False
Fail to Reject the
Null Hypothesis

16. Educational Research 2e: Creswell
Other inferential tests
• Confidence intervals
• Effect sizes

17. Educational Research 2e: Creswell
How do you report the
results?
• Tables summarize statistical information
• Figures (charts, pictures, drawings)
portray variables and their relationships
• Detailed explanations about statistical
results

18. Educational Research 2e: Creswell
How do you discuss the
results?
• Summarize major results
• Explain why they occurred
• Advance limitations
• Suggest future research