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My Peds Prep > Stats > Flashcards

Stats Flashcards

1
Q

Which type of test has few false negatives, or negative test results are reliable?

A

Sensitive

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2
Q

Which type of test could have lots of false positives, making positive results not as reliable?

A

Sensitive

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3
Q

What type of test is a good screening test?

A

Sensitive

*Negative rules out disease, but positive doesn’t necessarily rule in disease

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4
Q

What test has reliable negative and no false positives?

A

Sensitive

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5
Q

What type of test has positive results that are very reliable, but false negatives can occur?

A

Specific

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6
Q

What type of test can be used to determine treatment since positive results are reliable?

A

Specific

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7
Q

What is a common example of a specific test used in peds?

A

Rapid strep- Positive you can trust and treat, negative you send for culture

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8
Q

What type of test has reliable positives with rare false positives?

A

Specific

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9
Q

What is the sensitivity of a test?

A

The probability that the test will produce a true positive result when used on the population with the disease

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10
Q

What is the equation for sensitivity?

A

TP/(TP + FN)

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11
Q

True or False: In a test with high sensitivity, positive results may not be reliable

A

True

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12
Q

Negative results in what type of test can rule our disease?

A

Sensitive (very few false negatives)

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13
Q

What type of test is a good screening test?

A

Sensitive (if negative, probably true negative and no further workup needed)

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14
Q

Negative results are reliable in what type of test?

A

Sensitive

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15
Q

What is the equation for specificity?

A

TN/(TN + FP)

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16
Q

What is the specificity of a test?

A

Probability that is will produce a true negative result when used on a population without disease

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17
Q

What type of test has very few false positives?

A

Specific

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18
Q

In what type of test are positive results reliable?

A

Specific

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19
Q

What type of test will have very few false negatives?

A

Specific

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20
Q

A specific test is good for what?

A

To confirm the presence of a disease

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21
Q

In assessment for stroke, what type of test is a head CT?

A

Specific: If positive, helps to diagnose acute stroke, if negative still need further workup like MRI, ect. (may be false negative)

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22
Q

What test is good for confirming positive disease?

A

High specificity

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23
Q

A test with good positive and negative predictive values is what (in terms of sensitivity and specificity)?

A

Sensitive enough to minimize false negatives

Specific enough to minimize false positives

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24
Q

What is the positive predictive value of a test?

A

Probability that someone who tests positive actually has the disease and doesn’t represent a false positive.

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25
Q

What is the equation for positive predictive value?

A

TP/(TP + FP)

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26
Q

When is positive predictive value most useful?

A

When prevalence is high

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27
Q

What happens to positive predictive value as prevalence increases?

A

Positive predictive value increases

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28
Q

What happens to positive predictive value as prevalence falls?

A

Positive predictive value falls

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29
Q

True or False: The higher the positive predictive value, the higher the reliability of a positive result

A

True

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30
Q

What is negative predictive value?

A

The probability that someone who tests negative is actually disease free and doesn’t represent a false negative

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31
Q

When is negative predictive value most useful?

A

When prevalence if low

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32
Q

What happens to negative predictive value as prevalence increases?

A

Negative predictive value falls

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33
Q

What happens to negative predictive value as prevalence falls?

A

Negative predictive value increases

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34
Q

True or False: A high negative predictive value increases the reliability of negative result

A

True

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35
Q

If you are testing a group where a specific disease is prevalent, will the negative predictive value for that disease be lower or higher?

A

Lower

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36
Q

What is the equation for negative predictive value?

A

TN/(TN + FN)

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37
Q

What is the null hypothesis?

A

That results obtained were due to chance factors and not the variables being studied

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38
Q

What is generally a synonym to “rejecting the null hypothesis”?

A

“Statistically significant”

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39
Q

What is generally the goal of research in terms of a null hypothesis?

A

To reject the null hypothesis

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40
Q

What is the P value?

A

The chance that the null hypothesis was rejected in error

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41
Q

What represents the odds that the null hypothesis was correct and that the results were due to chance and not attributed to the studied variables?

A

P

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42
Q

What does a p value <0.01 mean?

A

Less than 1% chance that the null hypothesis was rejected in error and results are due to chance alone

43
Q

What P value is significant enough to reject the null hypothesis?

A

P < 0.05

44
Q

True or False: The lower the P value the more significant the study?

A

True

45
Q

What is a type 1 error?

A

Rejecting the null hypothesis in error- thinking something was significant/different when it really wasn’t

46
Q

What is the probability of a type 1 error?

A

P-value

47
Q

What is it called if you labeled an insignificant study as significant?

A

Type 1 error (study was “overestimated”)

48
Q

What is a type 2 error?

A

Where you rejected the null hypothesis in error

49
Q

What is it called if you determined that the findings could occur by chance and accepted the null hypothesis when in reality they should have been attributed to the study variables?

A

Type 2 error

50
Q

What is it called if you labeled a significant study as insignificant?

A

Type 2 error (study was “underestimated”).

51
Q

In most cases of medicine, which is worse, a Type 1 or Type 2 error?

A

Type 1

52
Q

In research, what addresses whether an instrument or test actually measured what it intended to measure?

A

Validity

53
Q

What in research refers to the consistency or repeatability of scores>

A

Raliability

54
Q

What does an intentention to treat analysis insist on?

A

That all patients remain in the original groups to which they were initially randomly assigned in the study

55
Q

How does an intention to treat analysis help maintain power in a study?

A

If patient can be moved to another group as study progresses, benefits of original randomization process would be lost and bias would creep in

56
Q

What is number needed to treat?

A

The number of patients that you would need to treat to prevent one additional adverse effect

57
Q

True or False, depending on your study group characteristics, the NNT changes?

A

True

58
Q

What is the equation for NNT?

A

NNT = 1/ARR

ARR = Rate in untreated group - Rate in treated group

59
Q

What is the number of newly diagnosed cases of a disease in a period of time?

A

Incidence

60
Q

What is the total number of cases of disease existing in a population?

A

Prevalence

61
Q

What is a measure of the spread of individual values around the mean or average value?

A

Standard deviation

62
Q

What does standard error describe?

A

How accurate the sample mean value used in the analysis is compared to the “true” population mean value

63
Q

True or False: The close the sample mean is to the “true” mean, the more accurate the study results are

A

True

64
Q

What is the confidence interval a measure of?

A

The reliability of your result

65
Q

What does confidence interval consist of?

A

Range of values in which you are confident that the true population result will be found

66
Q

In applied practice, what confidence level are confidence intervals typically stated at?

A

95%

67
Q

What does a confidence interval stated at the 95% confidence level mean?

A

The level at which you are 95% confident that your result lies within the true result of the general population

68
Q

True or False: Greater levels of variance within a population yield larger confidence intervals and therefore less precise estimates of the measure

A

True

69
Q

What does statistically significant mean?

A

The results have a small chance of having occurred by chance alone

70
Q

True or False: Statistically significant implies clinical importance

A

False

71
Q

What is pre-test probability?

A

Best estimate of the probability that a condition is present before you start diagnostic testing

72
Q

What helps to establish post-test probability of a suspected condition?

A

Diagnostic test result

73
Q

What is a likelihood ratio of a test?

A

The likelihood that a person who has the condition will have a positive test result

74
Q

What indicates by how much the result of the test will raise or lower your pre-test probability and get you closer to the post-test probability?

A

Likelihood ratio

75
Q

What is the difference between positive predictive value and pre-test probability?

A

PPV applies to the test and Pre-test Probability applies to the condition

76
Q

What does a likelihood ratio greater than 1 do?

A

Increases the probability that the target condition is present

77
Q

What does a likelihood ratio under 1 do?

A

Makes the target condition less likely

78
Q

How is the absolute risk of developing a condition calculated?

A

Divide the number of patients who develop disease by the total patients exposed

79
Q

What does relative risk compare?

A

The probability of an outcome in the exposed group to the probability of the outcome in an unexposed group

80
Q

What does an odds ratio represent?

A

The odds of an outcome in one group compared to the odds of that outcome in another group

81
Q

Best practice in medical care is derived from what?

A

Evidence based care

82
Q

Rank the 5 types of research studies from most valid to least valid

A
  1. Randomized, controlled trials
  2. Cohort studies
  3. Case-control studies
  4. Cross-sectional studies
  5. Case studies
83
Q

What is considered the gold standard of research designs?

A

Randomized controlled trials

*Study participants are assigned randomly to one treatment or another

84
Q

What are 2 major strengths of a randomized controlled trial?

A
  1. The minimialization of confounding variables by making the baseline groups equivalent
  2. Usually blind to participants and those administering the study
85
Q

True or False: Randomized controlled trials reduce the expectation of bias of the patient and reduce bias in interpreting the results

A

True

86
Q

What are limitations of randomized controlled trials?

A

Cost and time

87
Q

What type of study follows a group forward or traces then backwards to investigate associated risks for a certain outcome?

A

Cohort

88
Q

What are limitations of cohort studies?

A

Require large sample size, possible confounding variables

89
Q

When are case-control studies useful?

A

When you only have a small sample size or a rare outcome

90
Q

How does a case-control study work?

A

You start with patients with the disease and then patients without the disease and search for risk factors

91
Q

What timing component is important for a case-control study?

A

The risk factor has to come in time before the outcome

92
Q

What are limitations of case-control studies

A

Small sample size, risk of confounding variables

93
Q

What type of study is observational and great at looking at associations between two measured factors at one point in time

A

Cross-sectional studies

94
Q

True or False: Cross-sectional studies look at measures over time

A

False

95
Q

What are limitations of a cross-sectional study?

A

Risk of confounding variables and results cannot be used to infer causality

96
Q

What type of study involves studying the same group of individuals over an extended period of time?

A

Longitudinal

97
Q

What are 2 types of studies based on individual outcomes

A
  1. Case reports
  2. Anecdotal reports

*Limited because they have many confounding variables

98
Q

What uses a well-defined approach to locate and summarize articles related to a clinical question?

A

Systematic review

99
Q

What 4 things do systematic reviews require?

A
  1. Specific clinical question
  2. Thorough search for studies
  3. Clear explanation for which studies were considered and which were not
  4. Descriptive results section summarizing the findings
100
Q

What does a meta-analysis do?

A

Pools all the statistical results collected from a group of articles

101
Q

Name 7 things a meta-analysis should do

A
  1. Specific clinical question
  2. Thorough search for studies
  3. Clear explanation for which studies were considered and which were not
  4. Descriptive results section summarizing the findings
  5. Present a summary statistic using data from all included studies
  6. Report whether combining statistics was possible
  7. Assess for publication bias
102
Q

What is publication bias?

A

When some studies weren’t published, but would have affected the data

103
Q

Which is better, systematic review or meta-analysis?

A

Meta-analysis

104
Q

What is a limiting factor for both meta-analysis and systematic review?

A

Conclusions in both are based on data collected outside of your control

My Peds Prep (34 decks)

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