sahs biostatistics

8/14/2019 SAHS BIOSTATISTICS

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SAHS BIOSTATISTICS

TUTORIALS

DNA



In a study of iron deficiency amonginfants,

random samples of infantsfollowing different

feeding programs were compared.

One groupcontained breast-fed infants, whilethe children

in another group were fed by astandard baby

formula without any iron

supplements.



Here are summary results of bloodhemoglobin levels at 12 months of

age.

Group N X SD

Breast-fed 8 13.3 1.7Formula-fed 10 12.4 1.8

1.State the null hypothesis

2.State the alternate hypothesis

3.State the appropriate teststatistic to use

4.Test at 95% level of significance

whether the two feeding



Trace metals in drinking water wellsaffect the flavor

of the water and unusually highconcentrations can

pose a health hazard. Furthermore,

the water in wellmay vary in the concentration of thetrace metals depending upon from

where it is drawn. Trace metalconcentrations (mg/L) on zinc werefound from

water drawn from the bottom and the



Location Bottom Top

1 .430 .4152 .266 .238

3 .567 .390

4 .531 .410

5 .707 .

605




2.State the alternatehypothesis

3.State the appropriate teststatistic to use

4.Test at 95% level of

significance whether thetrace metal concentration of zinc at the two levels be

significantly different.



A survey was conducted toinvestigate the

severity of rodent problems in eggand poultry

operations. A random sample of

operators wasselected, and the operators wereclassified

according to the type of operationand the extent

of the rodent population. A total of

78 egg




2.State the alternate hypothesis

3.State the appropriate test statisticto use

4.Test at 95% whether there is any

association between the type of operation and the extent of rodent population.



Restenosis– narrowing of the bloodvessels – frequently occurs aftercoronary angioplasty, but accurate

prediction of which individuals willhave this problem is problematic. In astudy conducted in 1993, the

investigators hypothesized thatrestenosisis more likely to occur if activated smooth-muscle cells incoronary lesions at the time of surgery are present. They used thenumber of reactive nuclei in thecoronary lesions as an indicator of the

presence of the activated smooth-

P ti t D f St i (%) t N b f R ti N l i



Patient Degree of Stenosis (%) atFollow-up

Number of Reactive Nucleiat Initial Surgery

1 28 52 15 3

3 22 24 93 105 60 126 90 257 42 8

8 53 39 72 1510 0 1311 79 1712 28 0

13 82 1314 28 1415 100 1716 21 1



1. Construct a scatter plot for thesedata.2. Using the least squares method,find the best fitting linear relationshipbetween number of reactive nuclei inthe lesions and the degree of stenosis.

3. Interpret the slope and intercept interms of the problem.4. What is R2 for this regression andinterpret your results.

5. What is the expected degree of stenosis for a new subject whopresents with number of reactivenuclei in the coronary lesions equal to

33?

sahs biostatistics

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