Welcome to

Rectangularity!

Home of the Squarely Quads

Rectangularity has a population of 100 squarely quads with various areas. Each square

represents one unit towards a rectangle’s area.

What is the purpose of a confidence interval?

To determine how confident you are that the population

mean falls within your interval

Why are we replacing the card after each selection?

to maintain independence among the sample

observations

Confidence Interval Formula

CI = x ± MEME = z * (σ/√n)critical z value

1. percent of area in each tail = (1 – CI)/22. 2nd, VARS, 3 (invNorm), 1-%

Table of Common Confidence and Levels

1 /2 z/2

0.70 0.30 0.15 1.03

0.75 0.25 0.125 1.15

0.80 0.20 0.10 1.28

0.90 0.10 0.05 1.645

0.95 0.05 0.025 1.96

0.99 0.01 0.005 2.58

Confidence Intervals on TI-841. S2. > twice “Tests”3. 7 (Zinterval…)4. > once “Stats”5. ; once & enter σ (s if unknown)6. ; once & enter x7. ; once & enter n8. ; once & enter CI (as a decimal)9. ; once & e

0 1 2 3 4 5 6 7 8 9 10 11 12 13

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An 80% confidence level means that we would expect 80% of the interval estimates to include the population parameter.

99%

A 99% confidence level means that we would expect 99% of the interval estimates to include the population parameter.

It is very likely to enclose the mean of the population.

It may be too wide to give us a good estimate of the value of μ.

Cardsto represent

the Populationof Squarely Quads

Mr.1

Mr.3

Mr.5

Mr.7

Ms. 2

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Ms. 6

Ms. 8

Mr. 9 Mr. 11

Mr. 13

Mr. 15

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Mr. 17

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Mr. 25

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