Intro to Biostatistics and Descriptive Statistics

Question 1

Biostatistics

Answer 1

Biology and Statistics
The statistics of medicine, health sciences, and public health

Question 2

Components of Biostatistics

Answer 2

Descriptive statistics, probability, estimate population parameters, and hypothesis testing

Question 3

Accessible Population

Answer 3

The actual population of subjects available to be chosen for a study (a subset of the target population)

Question 3

Target Population

Answer 3

The larger population to which results of a study will be generalized

Question 3

Sample

Answer 3

A subgroup of the population of interest (accessible population) which allows the results of research to be “generalized” to the population

Question 3

Population

Answer 3

The entire set of people in the group of interest. Statistical characteristic is a parameter

Question 3

Descriptive Statistics

Answer 3

Used to describe a sample shape, central tendency, and variability

Question 3

Inferential Statistics

Answer 3

Used to make inferences about a population

Question 3

Descriptive Statistics are used to characterize…

Answer 3

Shape, Central tendency, and variability

Question 4

Central Tendency

Answer 4

The “central” value
The BEST representative value of the target population value
“The statistical measure that identifies a single value as representative of an entire distribution”

Question 5

Variability

Answer 5

The spread of the data

Question 6

Frequency

Answer 6

The number of times a value appears in a data set

Question 7

Frequency Distribution

Answer 7

The pattern of frequencies of a variable
Can be summarized in a table (screen for outliers)

Question 8

Mean

Answer 8

Average
Best choice for numeric, symmetrically distributed data
Not good for skewed data because it is affected by extreme scores

Question 9

Median

Answer 9

The score at which 50% of the scores are above and below
Divides scores in two equal halves
Best for non-symmetrical data
Not effected by extreme scores

Question 10

Mode

Answer 10

The score that occurs most frequently
Limited utility; nominal or ordinal data
Common in surveys

Question 11

Advantages of Mean

Answer 11

Easy to calculate and interpret
Don’t need to arrange values in order
Not prone to bias
All values are represented
All algebraic formulas are possible

Question 12

Disadvantages of Mean

Answer 12

Can’t be used with categorical data
Can’t be calculated if data are missing
Affected by extreme values

Question 13

Median Advantages

Answer 13

Easy to calculate
Not affected by extreme value
Can be used with “ranked” data

Question 14

Median Disadvantages

Answer 14

Tedious in a large data set
Problematic with even number of observations
Doesn’t account for all values

Question 15

Mode Advantages

Answer 15

Easy to understand and calculate
NOT affected by extreme values
Easy to identify in a data set and in a frequency distribution
The mode is useful for categorical data

Question 16

Mode Disadvantages

Answer 16

Not defined when there are no repeats in a data set
Not based on all values
Unstable when the data consists of a small number of values
Sometimes the data have 2+ modes, or no mode at all

Question 17

Distribution Skewed to the Right

Answer 17

The “tail” faces right; not where the bulk of the curve lies
AKA “positive skew”
Mean > Median/Mode

Question 18

Distribution Skewed to the Left

Answer 18

The “tail” faces left
AKA “negative skew”
Mean < median/mode

Question 19

Range

Answer 19

Difference between highest and lowest score

Question 20

Percentiles

Answer 20

A score’s position within the distribution (divides distribution into 100 parts)

Question 21

Quartiles

Answer 21

Divides distribution into 4 equal parts

Question 22

Box Plots

Answer 22

Graphical distribution using median, range, and IQR
Displays a five-number summary of a data set
Box = interquartile range
Horizontal line at median
“Whiskers” = minimum and maximum scores

Question 23

Standard Deviation

Answer 23

Most common measure of validity in clinical literature
Reported in same units as raw scores
Mean +/- SD or Mean (SD)

Question 24

Variance

Answer 24

Measure of validity is square of the standard deviation
Hard to understand variability in ROM scores when unit is degrees-squared

Question 25

Coefficient of Variation

Answer 25

Used for interval and ratio data only
Ration of SD to mean, expressed as percentage
Quantifies the precision of a technique
Unit-less, so is helpful comparing variability between two distributions on different scales

Question 26

Normal Distribution

Answer 26

Also known as a bell-shaped distribution or Gaussian Distribution
Symmetric around the mean
Constant and predictable characteristics
68% of the scores within +/- 1 SD of the mean
95% of the scores within +/- 2 SD of the mean
99% of the scores within +/- 3 SD of the mean

Question 27

Z-Scores

Answer 27

A standardized score based on the normal distribution
A score of 2 is interpreted as 2 standard deviations from the mean
Allows for the interpretation of a score in relation to the sample mean and variance