University of North Texas Dr. J. Kyle Roberts © 2004

Unit 4: Statistical Significance

Lesson 1: Constructing Confidence Intervals

EDER 6010: Statistics for Educational Research

Dr. J. Kyle Roberts

University of North Texas

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University of North Texas Dr. J. Kyle Roberts © 2004

Mean DifferencesIQ Scores

100 11585

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University of North Texas Dr. J. Kyle Roberts © 2004

Standard Error of the Mean

n

SDXX

SEMX Sample of IQ ScoresMean = 100SD = 15N = 25

325

15

QI

QI

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University of North Texas Dr. J. Kyle Roberts © 2004

Critical Values

-1.96 SD +1.96 SD

95% Confidence Intervals

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University of North Texas Dr. J. Kyle Roberts © 2004

Computing the CI95%

))((%95 XcvzXCI Sample of IQ ScoresMean = 100SD = 15N = 25

3QI

CI95% = 100 ± (1.96)(3)CI95% = 100 ± 5.88-or-CI95%: 105.88 – 94.12

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University of North Texas Dr. J. Kyle Roberts © 2004

What Does a CI Tell Me?CI95% = 100 ± 5.88

1. We are 95% confident that the interval around our obtained mean contains the population mean.

2. If we continued to sample from the population an infinite number of times, 95% of those sample means and confidence intervals would capture the population mean.

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University of North Texas Dr. J. Kyle Roberts © 2004

Confidence Intervals from a Population

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University of North Texas Dr. J. Kyle Roberts © 2004

Unit 4: Statistical Significance

Lesson 1: Constructing Confidence Intervals

EDER 6010: Statistics for Educational Research

Dr. J. Kyle Roberts

University of North Texas