Lesson 2 Flashcards
Things that we measure, count, or otherwise delineate
Variable
Types of Variable:
- Nominal
- Ordinal
- Interval
A variable can take on only a limited number of values, usually called categories. (or characters)
Nominal Scale
The variable takes on specific values that have some inherent order such as magnitude but without equivalent distances between categories.
Ordinal Scale
Where a variable takes on vlues in a quantitative range with defined differences between points
Interval Scale
It is already determined and so is not influenced by other factors
Independent Variable
Ex: Age, Gender, Temperature, and Time
Independent Variable
These are those things that might change in response to the independent variable
Dependent Variable
Ex: blood glucose concentration, enzyme activities, and the presence or absence of malignancy
Dependent Variable
It is a spread of data in which elements are distributed symmetrically around the mean, with most values close to the center
Gaussian (normal) distribution
Mean, median, mode
Gaussian (normal) distribution
These are statistical measures that are calculated based on the assumption that the data points follow Gaussian distribution and include parameters such as mean, variance, and standard deviation
Parametric statistics
t-test, ANOVA
Parametric statistics
ideal value for standard deviation
2SD
Describe what the magnitutde of results is and how the data points differ from one another
Descriptive Statistics
Meaning behind the numbers
Descriptive Statistics
A measure of how far apart they are disoersed from one another
Central Tendency
Measures of Central Tendency:
- Mean
- Median
- Mode
It is calculated by adding the values of all the individual data points and dividing that sum by the total number of data points
Mean
Used when the data are skewed so its calculation will not be affected by outliers
Median
Rarely used; most frequent observation
Mode
It is used to describe data with two centers (bimodal)
Mode
Measure of Speed:
- Range
- Standard Deviation
- Coefficient of Variation
- Variance
- SD index
- Simplest expression of spread of distribution
- It is the difference of highest and lowest score in a data
Range
- It is a measure of dispersion of values from the mean
- Helps describe the normal curve,
. A measure of distribution range
Standard Deviation
- A percentile expression of the mean
- An index of precision
Coefficient of Variation
- Called the SD squared
- Measure of variability
- It determins significant difference between griups of data
Variance
Is the difference between the value of a data point and the mean value divided by the group’s SD
SD index
Comparative Statistics:
- T-test
- F-test
Used to determine whether there is statistically significant difference between the means of two groups of data
T-test
Used to determine whether there is statistically significant difference between the standard of deviations of two groups of data
F- test
According to ____, “Quality is never an accident, it is always the result of high intention, sincere effort, intelligent direction and skillful execution, it represents the wise choice of many alternatives.”
Wiliam A. Foster
Reference range
Reference interval
A pair of medical decision points that span the limits of results expected for a defined healthy population
Reference interval
The upper and lower reference limits are set to define a specified percentage (usually 95%) of the values for a population
Reference interval
Range of values that include a specified probability usually 90% or 95%
Confidence interval
Confidence intervals serve to convey the variability of estimates and quantify the variability
Confidence interval
It is the interval that is computed to include a parameter such as the mean with a stated probability (commonly 90%, 95%, 99%) that the true value falls into that interval
Confidence interval
The application of reference intervals can be grouped into three main categories:
- Diagnosis of a disease or condition
- Monitoring of a physiologic condition
- Monitoring therapeutic drugs
- Inclusion and Exclusion criteria
- Essential to obtain the optimal set of specimens with an acceptable level of confidence
- Partitioning
Selection of Study Individuals
- controlled and standardized
- define the acceptable interferences
- extensive knowledge regarding the analyte, analytic parameters, methodology, and instrumentation
Pre-Analytical & Analytical Considerations
- Subject Preparation
- Prescription medications
- Collection time
- Sample storage
- Stress
- Food/ beverage ingestion
Pre-Analytic Factor
- Precision
- Accuracy
- Lot-to-lot reagents
- Linearity
- Interference
- Recovery
Analytical Factor
A study should at least have ____ individuals
120
T/F: Reference interval is calculated statistically using methods that depend on the distribution of the data
True
If normal, this method is used
Parametric
If not normally distributed, use the ___ method
non-parametric
Statistical test that assumes the observed values, or some mathematical transformation of those values, follow a normal (Gaussian distribution)
Parametric method
Defines the interval by the mean +/- 1.96 SDs
Parametric method
It is analyzed using percentiles
Non-Parametric method
Do not depend on the distribution
Non-Parametric method
The reference interval is determined by using the central 95% of values; the reference range is therefore defined by the _____
2.5th to the 97.5th percentiles
The reference interval is determined by using the central 95% of values; the reference range is therefore defined by the 2.5th to the 97.5th percentiles
Non-parametric method
Statistical test that makes no specific assumption about the distribution of data
Non-parametric method
Rank the reference data in order of increasing size
Non-parametric method
Because the majority of analytes are not normally (Gaussian) distributed, the recommended analysis for most reference range intervals
Non-parametric method
n =
number of intervals
2.5th percentile =
0.025 (n+1) 9
97.5th percentile =
0.975 (n+1)
Data analysis to verify a reference itnerval
Transference
The _____ allows less vigorous studies to verify a reference interval with as few as ___ subject specimens
CLSI; 20
Test method and subjects are the _____
similar
The nearness of closeness of the assayed value to the true of target value
Accuracy
Accuracy is estimated using three different types of studies:
- Recovery
- Interference Studies
- Patient Sample Concentration
The ability of an analytical method to give repeated results on the same sample that degree with one another
Precision
Determined by: Repeated analysis study
Imprecision
Determined by:
- recovery study
- interference study
- comparison of methods study
Inaccuracy
Is the ability of the analytical method to measure the smallest concentration of the analyte of interest
Analytical Sensitivity
Screening Test
Analytical Sensitivity
Is the ability of an analytical method to measure only the analyte of interest
Analytical Specificity
Confirmatory Test
Analytical Specificity
Ability of a test to detect a given disease or condition
Diagnostic Sensitivity
Ability of a test to correctly identify the absence of a given disease or condition
Diagnostic Specificity
The predictive value of a positive (PPV) test refers to the probability of an individual having the disease if the result is abnormal (“positive for the condition”)
Positive Predictive Value
refers to the probability that a patient does not have a disease if a result is within the reference range (test is negative for the disease)
Negative Predictive Value
