Estimation & Confidence Intervals

Estimation & Confidence Intervals

Now called "point estimate"

Build Confidence Interval around it

Confidence Intervals

General Formula:

[Point estimate ± Margin of Error]

Inferential Theory

σ unknown (t)

σ known (z)

proportion (z)

Considers dispersion, n & α

Why Care?

x̅1 = 100 with range of [5 to 195]

x̅2 = 100 with range of [90 to 110]

Examples

Titleist

Undergrad

Example

Inference Theory image

sigma unknown

sigma known

proportion

Finding Z-value

Finding Z-value

Finding t-value

Example

Example

Example

t-distribution

σ unknown

more conservative (wider interval)

2 components: α/2, df

Factors influencing Confidence Interval Width

Factors that influence width

vs.

Confidence in Point estimate

consideration in buildind CI

why care

Why Care Examples

construction of CI

Finding z value

problem sigma known

proportion problem

t-distn

Factors that influence width

t distn problem

All Rights Reserved by Brent Marinan & University of Arizona

Inference Theory

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Constructing C.I.'s

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