welcome to rectangularity ! home of the squarely quads
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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?. - PowerPoint PPT PresentationTRANSCRIPT
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
6.26
Clas
s Dat
afo
r 80%
Con
fiden
ce L
evel
0 1 2 3 4 5 6 7 8 9 10 11 12 13
6.26
Clas
s Dat
afo
r 99%
Con
fiden
ce L
evel
80%
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
Ms. 4
Ms. 6
Ms. 8
Mr. 9 Mr. 11
Mr. 13
Mr. 15
Ms.
10Ms.
12Ms.
14Ms.
16
Mr. 17
Mr. 19
Mr. 21
Mr. 23
Ms.
18Ms.
20Ms.
22Ms.
24
Mr. 25
Mr. 27
Mr. 29
Mr. 31
Ms.
26Ms.
28Ms.
30Ms.
32
Mr. 33
Mr. 35
Mr. 37
Mr. 39
Ms.
34Ms.
36Ms.
38Ms.
40
Mr. 41
Mr. 43
Mr. 45
Mr. 47
Ms.
42Ms.
44Ms.
46Ms.
48
Mr. 49
Mr. 51
Mr. 53
Mr. 55
Ms.
50Ms.
52Ms.
54Ms.
56
Mr. 57
Mr. 59
Mr. 61
Mr. 63
Ms.
58Ms.
60Ms.
62Ms.
64
Mr. 65
Mr. 67
Mr. 69
Mr. 71
Ms.
66Ms.
68Ms.
70Ms.
72
Mr. 73
Mr. 75
Mr. 77
Mr. 79
Ms.
74Ms.
76Ms.
78Ms.
80
Mr. 81
Mr. 83
Mr. 85
Mr. 87
Ms.
82Ms.
84Ms.
86Ms.
88
Mr. 89
Mr. 91
Mr. 93
Mr. 95
Ms.
90Ms.
92Ms.
94Ms.
96
Mr. 97
Mr. 99
Ms.
98Ms.
100 Adap
ted
by D
r. Je
nnife
r L. B
row
n, C
olum
bus S
tate
Uni
vers
ity, 2
012
Orig
inal
Sou
rce:
(Ric
hard
son,
Cur
tiss,
Gab
rose
k, &
Rei
schm
an, 2
002)