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Pharmacy Biostatistics > The Descriptive Analysis > Flashcards

The Descriptive Analysis Flashcards

1
Q

What are Frequency Tables used for?

A

Used to present counts and frequencies of discrete or continuous data at any level of measurement

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2
Q

What are the components that must be included in a frequency table?

A

Clear title, descriptive column names, adequate space, and row/column delineation

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3
Q

What are Box and Whisker Plots used for?

A

Used to visualize the range or spread of data
Only 1 Axis is in mathematically meaningful units

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4
Q

What does the Box depict?

A

IQR (Qu - Ql), Median, and Mean

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5
Q

What does the Whiskers depict?

A

Min and Max values

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6
Q

What axis is the mathematically relevant one usually in Box and Whiskers?

A

Y-Axis

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7
Q

What are Bar Charts used for?

A

Used to graph discrete/categorical data

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8
Q

What are the bar charts ideal for visualizing?

A

Frequencies and Distributions, but not ideal for presenting trends over time

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9
Q

What are the components of a bar chart that must be included?

A

Title labeled axes with well defined units, columns NOT touching, aligned vertical or horizontal

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10
Q

What are Histograms used for?

A

Used to graph numeric data that have been apportioned into discrete categories

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11
Q

What are the components of a histogram that must be included?

A

Columns touching, title, labeled axes with well defined units

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12
Q

What do histograms usually illustrate?

A

Changes in a variable over time

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13
Q

What are Class Intervals?

A

Summarize by grouping the data into a set of contiguous, non-overlapping intervals, such that each value in the set of observations can be placed in one, and only one, of the intervals

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14
Q

How many class intervals do you use?

A

Too few = lose information
Too many = objective of summarization will not be met

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15
Q

What is the common rule of thumb for class intervals?

A

No fewer than 6 intervals but no more than 15, intervals should be the same length

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16
Q

What is a Frequency Polygon?

A

Line graph in which we place a dot above the midpoint of each class interval and connect the dots

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17
Q

How does a Frequency Polygon look?

A

Begin and End with the line touching the X-Axis
Each group is represented with a different line

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18
Q

What are Pie Charts?

A

Used to represent proportions or relative quantities of values

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19
Q

What is the definition of Proportion?

A

The number of observations with a given characteristic divided by the total number of observations in a given group

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20
Q

How to calculate proportion?

A

Take the variable you are interested in and divide it by the total

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21
Q

What is the Rate?

A

Similar to proportion but competed over a SPECIFIC time-period and use a MULTIPLIER aka the base

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22
Q

What is Incidence?

A

Measure of Morbidity
Measures the number of new cases of a disease/symptom/problem that develops in a population risk within a given period of time

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23
Q

What is Prevalence?

A

Measure of Morbidity
Measures the probability of having a disease at a point in time
Reflects existing disease within the population

24
Q

What does prevalence represent best?

A

Represents the best estimate of the probability of the presence of disease before evaluation and individual’s history, physical exam, or lab tests

25
Q

What is POCT?

A

Point of Care Testing

26
Q

Standard Two by Two Table Set Up

A

W X
Y Z

27
Q

What do the variables mean in a 2 by 2 table?

A

W: true positive, patients with condition and tested positive
X: false positive, patients w/o condition and tested positive
Y: false negative, patients with condition and tested negative
Z: true negative, patients w/o condition and tested negative

28
Q

What is the false positive rate?

A

Number of false positive results divided by all patients who do not have the disease

29
Q

How do you calculate the false positive rate?

A

(X) / (X+Z)

30
Q

What is the false negative rate?

A

Number of false negative results divided by all patients with the disease

31
Q

How do you calculate the false negative rate?

A

(Y) / (W+Y)

32
Q

What is Sensitivity?

A

The ability of a diagnostic test to correctly identify individuals with disease
Proportion of individuals with the disease who are correctly identified by the test

33
Q

How do you calculate the sensitivity?

A

(W) / (W+Y)

34
Q

What is sensitivity also known as?

A

True positive rte
High sensitivity with low false negative rates

35
Q

What is Specificity?

A

The ability of a diagnostic test to correctly identify individuals without disease
Proportion of individuals without the disease who are correctly identified by the test as disease-free

36
Q

How do you calculate the specificity?

A

(Z) / (X+Z)

37
Q

What is specificity also known as?

A

True negative rate
High specificity with low false positive rates

38
Q

What is the Predictive Value?

A

How likely it is that the individual does or does not have the disease give their test result

39
Q

What is a Positive Predictive Value?

A

Probability that a patient has the disease given that a positive test result was obtained

40
Q

How do you calculate the positive predictive value?

A

(W) / (W+X)

41
Q

What is a Negative Predictive Value?

A

Probability that a patient does not have the disease given that a negative test result was obtained

42
Q

How do you calculate the negative predictive value?

A

(Z) / (Y+Z)

43
Q

What are predictive values affected by?

A

Prevalence of the disease in the population of interest

44
Q

Ex. A research study evaluated the use of saliva tests for COVID. 60 patients with the virus confirmed by PCR were evaluated. 40 patients without the virus were also included. The saliva test results were positive in 40 pts with the virus and in 10 in the pts without the virus. How do you set up the table?

A

W: 40 X:10
Y: 20 Z: 30

45
Q

What are ROC Curves?

A

Receiver Operating Characteristic Curves

46
Q

What are ROC Curves used for?

A

To illustrate the trade-offs between sensitivity (true positive rate) and the false positive rate

47
Q

What do the points on the ROC curve represent?

A

Each point on the ROC curve represents the sensitivity and false positive rate at a different decision thershold

48
Q

What does the Y Axis represent on the ROC?

A

True positive rate = Sensitivity

49
Q

What does the X Acid represent on the ROC?

A

False positive rate

50
Q

What does 0,0 represent on the ROC?

A

Represents 0% sensitivity and 0% false positive rate, all test results are negative for disease

51
Q

What does 1,1 represent on the ROC?

A

Both the sensitivity and false positive rates are 100%, all test results are positive for disease

52
Q

What is the Chance Diagonal?

A

Connects 0,0 to 1,1 in a straight line

53
Q

What the does the Chance Diagonal represent?

A

No ability to discriminate between patients with disease vs. those without disease

54
Q

Where does the ROC Curve need to lie to have some diagnostic ability?

A

ABOVE the Chance Diagonal

55
Q

What is area under the ROC?

A

Allows for comparisons of different diagnostic tests

56
Q

What is the area under the Chance Diagonal?

A

0.5

57
Q

What is the area under the ROC for a perfect diagnostic test?

A

1

Pharmacy Biostatistics (17 decks)

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