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Physiology MRCP > Statistics > Flashcards

Statistics Flashcards

1
Q

What is sensitivity?

A

Proportion of patients who have condition who have positive test result

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2
Q

How is sensitivity calculated?

A

True positive / true posoitive + false negative (all patients with condition)

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3
Q

What is specificity?

A

Proportion of patients without condition who have negative test result

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4
Q

How is specificity calculated?

A

True negative / true negayive + false positive (all patients without condition)

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5
Q

What is positive predictive value?

A

Chance patient has condition if diagnostic test is positive

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6
Q

How is positive predictive value calculated?

A

True positive / true positive + false positive

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7
Q

What is negative predictive value?

A

Chance patient does not have condition if diagnostic test is negative

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8
Q

How is negative predictive value calculated?

A

True negative / true negative + false negative

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9
Q

What is likelihood ratio for positive result?

A

How much odds of disease increase with positive test result

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10
Q

How is the likelihood ratio for a positive test result calculated?

A

Sensitivity / (1-specificity)

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11
Q

What is the likelihood ratio for a negative test result?

A

How much odds for a disease decrease with a negative test result

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12
Q

How is likelihood ratio for a negative test result calculated?

A

(1-sensitivity) / specificity

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13
Q

What is a null hypothesis?

A

States no difference between 2 groups

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14
Q

What is an alternate hypothesis?

A

States there is a difference between groups

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15
Q

What is a type 1 error when testing null hypothesis?

A

Null hypothesis is rejected when null hypothesis is actually true
(saying there’s a difference when there’s not)

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16
Q

What is the probability of making a type 1 error?

A

Alpha

17
Q

What is a type 2 error when testing a null hypothesis?

A

Null hypothesis accepted when it is false

18
Q

What is the probability of making a type 2 error?

A

Beta

19
Q

What is the p value?

A

Assuming null hypothesis is true, p value is probability of obtaining a result by chance at least as extreme as one observed

20
Q

What is the power of a study?

A

Probability of correctly rejecting null hypothesis when it is false

21
Q

How is the power of a study calculated?

A

1 - beta (probability of making type 2 error )

22
Q

What are the 2 types of significance tests?

A

Parametric tests - for quantitive data in normal disturbution (mean=median=mode)
Non parametric - if qualitative data or shewed distrubution

23
Q

What are the types of parametric significance tests?

A

Student’s T test
Pearson product-moment coefficient - shows correlation

24
Q

What are the types of non parametric tests?

A

Mann-Whitney U test
Wilcoxon signed rank test
chi-squared test
Spearman or Kendall rank

25
Q

What does Mann Whitney U test do?

A

Compares ordinal, interval or ratio scales of unpaired data

26
Q

What does Wilcoxon signed rank test do?

A

Compares 2 sets of observations on single sample before and after intervention

27
Q

What does chi-squared test do?

A

Compare proportions or percentages

28
Q

What does Spearman or Kendall rank show?

A

Correlation

29
Q

What is reliability?

A

Consistency of measure

30
Q

What is validity?

A

Accuracy of measure

31
Q

What is relative risk?

A

Ratio of Experimental event rate to control event rate

32
Q

How is relative risk calculated?

A

EER / CER

33
Q

How is is relative risk reduction or increase calculated?

A

Dividing absolute risk change by control event rate
(EER-CER) / CER

34
Q

What is a confidence interval?

A

Range of values within which the true effect of intervention is likely to lie

35
Q

What is the standard error of the mean?

A

Measure of th spread for the mean of the observations ie how accurate calculated sample mean is from true population mean

36
Q

How is standard error of the mean calculated?

A

SEM = standard deviation / square root of sample size

37
Q

How is a 95% confidence interval calculated?

A

Lower limit = mean - (1.96 x standard error of mean)
Upper limit = mean + (1.96 x standard error of the mean)

Physiology MRCP (19 decks)

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