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Decreased Rate of Coronary Restenosis After Lowering of Plasma Homocystine Levels. Seminar 25 Elise Miller. A few definitions…. Plasma Homocystine- blood amino acid influenced by genetics and diet. Restenosis- renarrowing of an artery after angioplasty caused by fat or cholesterol buildup.

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Decreased Rate of Coronary Restenosis After Lowering of Plasma Homocystine Levels


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decreased rate of coronary restenosis after lowering of plasma homocystine levels

Decreased Rate of Coronary Restenosis After Lowering of Plasma Homocystine Levels

Seminar 25

Elise Miller

a few definitions
A few definitions….
  • Plasma Homocystine- blood amino acid influenced by genetics and diet.
  • Restenosis- renarrowing of an artery after angioplasty caused by fat or cholesterol buildup.
  • Angioplasty- opens blocked arteries by the inflation of a tiny balloon.
which alternative makes sense
Which Alternative Makes Sense?

Luminal Diameter:

Ha: µF>µP Ha: µF<µP

Stenosis:

Ha: µF>µP Ha: µF<µP

Late Loss Luminal Diameter:

Ha: µP>µF Ha: µP<µF

t test construction
T-test Construction
  • When dealing with two means and unequal sample sizes:
degrees of freedom
Degrees of Freedom
  • Large, complicated formula….

d.f.= (s12/n1 + s22/n2) ÷ (((s12/n1)2 ÷ (n1-1)) + ((s22/n2)2 ÷ (n2-1)))

  • For our purposes it is assumed that df=160

(somewhere between n1-1 and n1+n2-2)

practice
Practice
  • Find the T-statistic for Luminal Diameter
  • Given info:

Folate Group: sample n= 92

sample mean= 1.72

sample s.d= .76

Placebo Group: sample n=85

sample mean=1.45

sample s.d= .88

plug in the values
Plug in the values…

(1.72-1.45)/sqrt[(.76^2/92)+(.88^2/85)]

t=2.1765

  • This value gets inputted into Minitab to easily find the P-value.
t values
T-Values
  • Luminal Diameter:

T=2.1765

  • Stenosis:

T=-2.226

  • Late Loss Luminal Diameter:

T=-1.860

reasoning
Reasoning…
  • Luminal Diameter:

-positive value, wider arteries are better

  • Stenosis:

-Negative value, after treatment the severity of stenosis decreased.

  • Late Loss Luminal Diameter:

-Negative value, control is being compared to treatment group

-the negative shows that the luminal diameter was smaller in the control group.

what about the p values
What about the P-values?
  • Based on the t-statistics, what may the p-values be? (large n value)
      • Luminal Diameter:

T=2.1765

      • Stenosis:

T=-2.226

      • Late Loss Luminal Diameter:

T=-1.860

p value comparisons
P-value Comparisons
  • Luminal Diameter:

given: p=.02 by hand: p=.0155

  • Stenosis:

given: p=.01 by hand: p=.01371

  • Late Loss Luminal Diameter:

given: p=.03 by hand: p=.0324

potential bias
Potential Bias?
  • Most studies published in medical journals tend to have little or no bias
  • A few people did drop out of the study, but most likely did not create any impact on the results.
research conclusions
Research Conclusions
  • Folate treatment is beneficial compared to placebo treatment group.
  • Treatment reduced restenosis, and late loss luminal diameter.
  • Treatment increased luminal diameter post-op.