Biostatistics Practice2

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Biostatistics Practice2
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Example A study shows that 70 of all patients
coming to a certain medical clinic have to wait
at least fifteen minutes to see their doctor.
What is the probability that among ten patients
coming to this clinic (a) 3 patients will wait
(b) more than 8 patients will wait at least
fifteen minutes to see their doctor?
P(A) p 0,70
(a)
(b)
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Example The number of emergency calls which an
ambulance service gets per day is a random
variable having th Poisson distribution with
l5,5. What is the probability that on any given
day it will receive (a) only 4 emergency calls,
(b) More than 4 emergency calls.
(a)
(b)
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Example A group of patients have a mean body
mass index (BMI) of 22 and a standard deviation
4. BMIs are approximately normally distributed. A
subject is classified as obese if his BMI has
greater than 30 BMI. In this group of patients
what is the propotion of obese patients? What is
the proportion of patients whose BMI less 18?
?22 ?4
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(No Transcript)
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Example It is known that 25 of the persons in
the study were obese. In this study, 200
individuals were examined and mean BMI score was
found as 23 and std. deviation was found as 5.
What is the cut-off point for obesity? What is
the number of the obese individuals?
Number of obese individuals 2000,25 50
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Example Scoring system was changed in ÖSS in
2003. The lowest score of the students who
attended Hacettepe University School of Medicine
was 195 in 2002, and 310 in 2003. It is also
known that, in 2002 mean160 s10, and in 2003
mean270 s15. Has the attendance score
increased in 2003?
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Sampling Distribution
Percent
Percent
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Example If the mean and standard deviation of
serum cholesterol values for male patients who
was diagnosed as having myocardial infarction are
240 and 40 mg/dl, what is the probability that a
random sample of 100 men will have a mean greater
than 250 mg/dl?
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In the previous example, instead of 100 men, if
we randomly select 16 men, what is the
probability of obtaining a sample mean greater
than 250 mg/dl?
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Example A researcher wants to estimate the
average serum cholesterol level of healty men.
Mean and standart deviation of the randomly
selected 100 men are 160 and 30 mg/dl.
95 CI for the population mean
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When the researcher selected 36 men at random,
95 CI for the population mean
90 CI for the population mean
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Example A researcher wants to estimate the
prevalence of osteoporosis in women over fifty
years of age. Among 100 randomly selected women,
15 women have a diagnosis of osteoporosis. What
is the 95 confidence interval for the proportion
of osteoporosis in women?
Point estimate of the proportion of osteoporosis
The standard error of the estimate is 0.036.
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95 CI for the population proportion
If a researcher wants to calculate interval for
the population proportion with 90 confidence