Post on 28-Dec-2015
Review Lecture
histograms, five number summary, one-sample confidence intervals, nonresponse, observational study
Kaiser Foundation Health Plan Company
Description from the Hoover’s Company website, a company that collects information on other companies
• “Kaiser Foundation Health Plan aims to be the emperor of the HMO universe. With more than 8.5 million members in nine states and the District of Columbia, it is one of the largest not-for-profit managed health care companies in the US. Kaiser has an integrated care model, offering both hospital and physician care through a network of hospitals and physician practices operating under the Kaiser Permanente name. Members of Kaiser health plans have access to hospitals and some 400 other health care facilities operated by Kaiser Foundation Hospitals and Permanente Medical Groups, associations consisting of about 13,000 doctors.”
Study of the Birth Weight of Newborns
• data collected on all pregnancies that occurred between 1960 and 1967 among women in the Kaiser Foundation Health Plan in the San Francisco – East Bay Area– 15000 families in the study
• a subset of 1236 chosen for a particular study on smoking and birth weight– born in one year of the study– lived at least 28 days– single birth
Caveats
• What is the reference population?
• Was there any random selection?
• Can a random sample be assumed?
Birth Weight in Ounces
Frequency
1601401201008060
100
80
60
40
20
0
Nonsmokers
Birth Weight in Ounces
Frequency
1601401201008060
70
60
50
40
30
20
10
0
Smokers
Birth Weight in Ounces
Frequency
1601401201008060
100
80
60
40
20
0
Smoking StatusNonsmokerSmokerUnknown
Nonresponse
• tends not to occur for lower birth weights– consequently this may
introduce some bias if the nonrespondents are all or mostly smokers
• only 10 nonrespondents out of 1236 cases– bias, if present, is small
Birth Weight in Ounes
Frequency
1601401201008060
3
2
1
0
Unknown Smoking Status
Smoking Status
Bir
th W
eig
ht
UnknownSmokerNonsmoker
175
150
125
100
75
50
Nonrespondents
Rank
Birth Weight
in Ounces
1 90 Minimum 2 106 3 108 Q1 4 115 5 126 128 Median
6 130 7 141 8 142 Q3 9 151
10 158 Maximum
193511421.5
57511081.5
511.5
34108142
3
1
IQRQ
IQRQ
IQR
IQR
Birth Weight in Ounces
Perc
ent
1601401201008060
14
12
10
8
6
4
2
0
Smoking StatusNonsmokerSmoker
Confidence Intervals
124.1) (122.0, 742
17.401.645123.05 99%
124.3) (121.8, 742
17.401.96123.05 95%
124.7) (121.4, 742
17.402.576123.05 99%
17.40 123.05 742
Nonsmokers
sxn
115.5) (112.8, 484
18.101.645114.11 99%
115.7) (112.5, 484
18.101.96114.11 95%
116.2) (112.0, 484
18.102.576114.11 99%
18.10 114.11 484
Smokers
sxn
90% Confidence Interval for the Proportion of Smokers
0.418) (0.372,
0.0231230
1
1230
744
1230
4861.645
4
)(1*
0.3951230
486
41226
2484
n
ppz
p
~~
~