1
PSY207
B
Spring 2011
Psychological Statistics
XII. Estimation
12.1 Overview
Estimation
• We have previously discussed testing hypotheses about a
population mean
• We may also be interested in estimating a population mean
• To determine the size of an effect
• How much will treatment affect the mean
• To determine information about a population
• We can use
sample characteristics
and
test statistics
(e.g.,
z
and
t
) to estimate population means
☻☻
☻☻
Hypothesis testing
Estimating population means
Is there a effect?
How much of the effect?
XII. Estimation
12.1 Introduction
12.2 Two Types of Estimates
Two types of Estimates
• Point estimates
• Use a single number to predict an unknown value
• Interval estimates
• Use a range of values to predict an unknown quality
• Confidence Intervals: the specific level of confidence/probability
the interval estimate comes with
• Based on
z
or
t

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