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Research Evaluation > Lecture 6 - Biostatistics Part 2-2 > Flashcards

Lecture 6 - Biostatistics Part 2-2 Flashcards

1
Q

Look at the table on slide 3… VERY IMPORTANT TO UNDERSTAND

A

Did you do it… seriously did you do it?

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2
Q

Measures of Central Tendency

A

Mean - the “average” – sum of the set divided by the number in the set

Median – the middle point (arrange the data smallest to largest, then find the middle point)

Mode – the score that occurs most frequently in a set of data
—–May have two most common values = “bimodal distribution”

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3
Q

quantifies the amount of variability, or spread, around the mean of the measurements.

To calculate: take each difference from the mean, square it, and then average the result

A

Variance (σ2 ):

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4
Q

a measure of variation of scores about the mean

A

Standard deviation (σ):

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5
Q

To calculate: take the √ of the variance

the “average distance” to the mean

A

Standard deviation (σ):

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6
Q

In practice, the standard deviation is used more frequently than the variance.
T or F?

A

True

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7
Q

Heterogeneous group vs homogeneous group?

A

When comparing two groups, the group with the larger standard deviation exhibits a greater amount of variability (heterogeneous) while the groups with smaller deviation has less variability (homogeneous).

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8
Q

Evaluates the strength of linear relationships or associations between variables

X increases and Y increases = positive correlation
X increases and Y decreases = negative correlation
0 is no correlation

A

Scatterplots

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9
Q

The statement that establishes a relationship between variables being assessed

Example: In a clinical trial the hypothesis states the new drug is better the placebo

A

Alternative hypothesis (Ha or H1)

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10
Q

The statement of no difference or no relationship between the variables

Example: In a clinical drug trial the null hypothesis states that the new drug is no better than placebo

A

Null hypothesis (Ho)

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11
Q

More important than p value – a better determination of significance

A

Confidence interval (CI)

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12
Q

Any statistic is simply an estimate of the true value of that statistic

A

Confidence interval (CI)

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13
Q

_____ produces a range within which the true value most likely lies

A

Confidence interval (CI)

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14
Q

95% CI states that we can be 95% certain that the “true” value is within the CI range

Meaning what is better?

A

Narrower CI is better

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15
Q

If the CI include 1 (null value) then the results are…

A

clinically insignificant

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16
Q

______ is used to separate from a large group of apparently well persons those who have a high probability of having the disease, so that they may be given a diagnostic work up, and if diseased can be treated.

A

A screening test

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17
Q

In general, screening is performed only when the following conditions are met:

A

The target disease is an important cause of mortality and morbidity.

A proven and acceptable test exists to detect individuals at an early stage of disease.

There is a treatment available to prevent mortality and morbidity once positives have been identified.

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18
Q

The proportion of people with the disease who have a positive test for the disease.

A

Sensitivity

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19
Q

The ability of the test to identify correctly those who have the test.

A

Sensitivity

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20
Q

– The proportion of people without the disease who have a negative test.

A

Specificity

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21
Q

The ability of the test to identify correctly those who do not have the disease

A

Specificity

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22
Q

A test with high _____ will not miss many patients who have the disease

A

sensitivity

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23
Q

A highly useful test when NEGATIVE

A

sensitivity

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24
Q

Screening test’s ability to identify presence of disease

A

Sensitivity

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25
Q

Tends to rule OUT the disease

A

Sensitivity

26
Q

High ____ means low probability of false negative

A

Sensitivity

27
Q

Screening test’s ability to truly identify absence of disease

That is, how likely is a negative test actually reporting the right answer?

A

Specificity

28
Q

A highly useful test when it is POSITIVE

A

Specificity

29
Q

Tends to rule IN the disease

A

Specificity

30
Q

High _____ means low probability of false positive

A

Specificity

31
Q

In practice, a compromise is reached and the cutoff point is set, leading to false-positives and false-negative results.

A

In a single test sensitivity may be increased but only at the expense of specificity, and similarly specificity may be increased at the expense of sensitivity.

32
Q

In a single test sensitivity may be increased but only at the expense of ______

A

specificity, and similarly specificity may be increased at the expense of sensitivity.

33
Q

A highly sensitive test is most useful to the clinician when it is

A

NEGATIVE

34
Q

A highly specific test is most useful to the clinician when it is

A

POSITIVE

35
Q

read slides 19-23 and make sure you can interpret the data correctly

A

it’s only your grade dummy

36
Q

Sequential (Two-Stage) Testing

Allows us to calculate the net sensitivity and net specificity of using both tests in sequence. After completing both tests there is a loss in…..

A

net sensitivity and net gain in specificity.

37
Q

in ________, a less ex­pensive, less invasive, or less uncomfortable test is generally performed first, and those who screen positive are recalled for further testing with a more expensive, more invasive, or more uncomfortable test, which may have greater sensitivity and specificity. It is hoped that bringing back for further testing only those who screen positive will reduce the problem of false positives.

A

Sequential (Two-Stage) Testing

38
Q

= proportion of patients who HAVE the disease and a positive test

A

Positive Predictive Value (PPV)

39
Q

= proportion of patients who DO NOT HAVE the disease, and have a negative test

A

Negative Predictive Value (NPV)

40
Q

Percent of patients with positive test who actually have the disease

A

Positive Predictive Value (PPV)

41
Q

Assesses reliability of positive test

i.e. PPV 90% = positive test 90% of the time the test is correct

A

Positive Predictive Value (PPV)

42
Q

With low prevalence (% of population) of disease:

A

Lower PPV
False positives increase
Less reliable positive test result

43
Q

Percentage of patients with a negative test who actually do NOT have the disease

A

Negative Predictive Value (NPV)

44
Q

Assesses reliability of a negative test

i.e. NPV 90% = negative 90% of the time the test is correct

A

Negative Predictive Value (NPV)

45
Q

With low prevalence(% of pop) of disease :

A

Higher NPV
False negative test decreased
A negative test result is more reliable

46
Q

________- the occurrence, rate, or frequency of a disease
Obtained from cohort studies
Must follow a cohort through time

A

Incidence

47
Q

Incidence is obtained from?

A

cohort studies in which a cohort was followed throughout time

48
Q

______the number of occurrences at one particular time

Obtained from cross-sectional studies

No time line, only a snap shot

A

Prevalence

49
Q

_____ is obtained from cross-sectional studies (no timeline)

A

prevalence

50
Q

slide 34…. Relationship between Incidence and Prevalence

A

understand it

51
Q

How does a treatment that prevents death effect incidence or prevalence?

A

the incidences don’t increase or decrease, but the prevalence does because people aren’t dying

52
Q

A method of predicting change in the dependent variable by changing one or more independent variables

A

Regression analysis

53
Q

Allows the researcher to explore the relationship between two continuous variables

A

Regression analysis

54
Q

What % of variation in the dependent variable can be explained by a change in the independent variable

A

Regression analysis

Example: when you GAIN 8 pounds, your SBP can be expected to increase by ~6 mmHg

Or, if you LOSE 8 pounds, your SBP can be expected to DROP by ~6 mmHg

55
Q

Four types of Data:

A 
Four types:
Categorical
---Nominal
---Ordinal
Continuous
---Interval
---Ratio
56
Q

Categorical Data

_____ named categories with no implied order

—-Gender, race, ABO blood type, group

A

Nominal

57
Q

Categorical Data

_____ sequenced or ranked data

—–Smallest to largest, lightest to heaviest, easiest to most difficult

A

Ordinal

58
Q

Continuous Data

_____ intervals along the scale are equal to one another (i.e. integers)

Set on an underlying continuum that allows you to talk about how much higher one value is than another

0 on the scale does not mean the absence of the item (e.g., degrees Fahrenheit)

A

interval

59
Q

Continuous Data

______ characterized by the presence of absolute zero on the scale

An absence of any of the trait being measured (e.g. weight)

Most precise

A

Ratio-

60
Q

what is the most precise form of data?

A

A ratio of continuous data

Research Evaluation (12 decks)

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