Summarizing Data

Question 1

Any characteristic that differs from person to person, such as height, sex, smallpox vaccination status, or physical activity pattern.

The value of a variable is the number or descriptor that applies to a particular person

Answer 1

Variable

Question 2

Epidemiologic database organized like a spreadsheet with rows and columns

Answer 2

Line listing

Question 3

Each row representing one person or case of disease

Answer 3

Record or observation

Question 4

Column contains information about one characteristic of the individual such as race or date of birth

Answer 4

Variable

Question 5

Categorical variable

Qualitative

Answer 5

Nominal

Ordinal

Question 6

Continuous

Quantitative

Answer 6

Interval

Ratio

Question 7

Categories without any numerical ranking such as county of residence

Alive or dead
Ill or well

Answer 7

Nominal scale

Question 8

Nominal variable with two mutually exclusive categories

Ill or well

Answer 8

Dichotomous

Question 9

Values that can be ranked but are not necessarily evenly spaced

Stage of cancer

Answer 9

Ordinal-scale variable

Question 10

Measured on a scale of equally spaced units, but without a true zero point such as date of birth

Answer 10

Interval-scale variable

Question 11

Interval variable with true zero point,

height in centimeters or duration of illness

Answer 11

Ratio-scale variable

Question 12

Where the distribution has its peak

Clustering at a particular value

Answer 12

Central location

Central tendency of a frequency distribution

Question 13

How widely dispered it is on both sides of the peak

Variation, dispersion

Distribution out from a central value

Independent of its central location

Answer 13

Spread

Question 14

Bell shaped curve

Answer 14

Normal distribution

Question 15

Three measures of central location

Answer 15

Mean
Median
Mode

Midrange
Geometric mean

Question 16

Third property of a frequency distribution where it may be asymmetrical or symmetric

Answer 16

Shape

Question 17

The tail of bell and not the hump

Answer 17

Skewness

Long tail to the left
Skewed to the left

Question 18

Distribution that has a central location to the left and a tail off to the right is said to be

Answer 18

positively skewed

skewed to the right

Question 19

Common in distributions that begin with 0

ex number of servings consumed, number of sexual partners

Answer 19

Skewed to the right

Question 20

Classic or symmetrical bell-shaped curve

Defined by a mathematical equation

Mean, median and mode coincide at the central peak but the area under the curve helps determine measures of spread such as the standard deviation and confidence interval

Answer 20

Normal distribution

Gaussian distribution

Question 21

Types of variable that may be summarized in ratio or proportion

Answer 21

Nominal
Ordinal
Interval
Ratio

Question 22

Types of variable where measures of central location may be employed

Answer 22

Interval

Ratio

Question 23

Types of variable where measures of central location may be employed

Answer 23

Interval

Ratio

Question 24

Provides a single value that summarizes an entire distribution of data

Answer 24

Measure of central location

Ave age of affected

Question 25

Selecting the best measure to use for a given distribution depends largely on two factors:

Answer 25

Shape or skewness of distribution | Intended use of measure

Question 26

Value that occurs most often in a set of data

Answer 26

Mode

Question 27

If the frequency distribution can have more than one mode

Answer 27

Bi-modal

Question 28

In a histogram, the mode is the

Answer 28

Tallest column

Question 29

Preferred measure of central location for addressing which value is the most popular or the most common Used almost exclusively as descriptive measure It is not typically affected by one or two extreme values (outliers)

Answer 29

Mode

Question 30

Middle value of a set of data that has been put into rank order Value that divides the data into two halves with one half of the observations being smaller than the median value and the other half being larger 50th percentile of distribution

Answer 30

Median

Question 31

Middle position =

Answer 31

(n+1)/2 If odd, middle position falls on single observation, median is the value of that observation If even, middle position falls between two observations, median equals the average of the two values

Question 32

Good descriptive measure for data that are skewed because it is the central point of distribution Not generaly affected by extremes (outliers)

Answer 32

Median

Question 33

Value that is closest to all other values in a distribution Add all observed values in the distribution Divide the sum by the number of observations

Answer 33

Mean

Question 34

When the mean is subtracted from each observation in the data set, the sum of these differences is zero Also called center of gravity Point at which the distribution would balance Not a good measure for severely skewed data or have extreme values in one direction or another Affected by extreme value because the mean uses all of the observations in the distribution

Answer 34

Centering property of the mean

Question 35

Halfway point or the midpoint of a set of observations Calculated as intermediate step in determining other measures Identify the smallest (minimum) observation and the largest (maximum) observation Add the minimum + maximum, then divide by two

Answer 35

Midrange

Question 36

Mean or average of a set of data measured on a logarithmic scale Used when the logarithms of the observations are distributed normally (symmetrically) rather than the observations themselves

Answer 36

Geometric mean

Question 37

Uses all data but not as sensitive to outliers as arithmetic mean

Answer 37

Geometric mean

Question 38

Most sensitive to outliers

Answer 38

Midrange

Question 39

Describe the dispersion (or variation) of values from that peak in the distribution

Answer 39

Measures of spread

Question 40

Measures of spread

Answer 40

Range Interquartile range Standard deviation

Question 41

Difference between its largest (maximum) value and its smallest (minimum value) From the minimim to maximum

Answer 41

Range

Question 42

Divide the data in a distribution into 100 equal parts 90th percentile has 90% of the observations at or below it

Answer 42

Percentile

Question 43

Messure of spread most commonly used with median Central portion of distribution from 25th to 75th percentile

Answer 43

Interquartile range

Question 44

Measure of spread used most commonly with the arithmetic mean Subtracting the mean from each observation The difference between the mean and each observation is squared to eliminate negative numbers Average is caculated and square root is taken to get back Variability of data

Answer 44

Standard deviation

Question 45

Calculated when the data is more-or-less normally distributed ie data fal into a typical bell shaped curve Recommended measure of spread

Answer 45

Standard deviation

Question 46

Variability we might expect in the arithmetic means of repeated samples taken from the same population Assumes that the data you have is actually a sample from a larger population Calculates confidence intervals around arithmetic mean

Answer 46

Standard error of mean

Question 47

Indicates a measurement’s precision Based on the mean itself and some multiple standard of error (variability of means that might be calculated from repeated samples from the same population)

Answer 47

Confidence interval

Question 48

Regardless of how data are distributed, means (particularly from large samples) tend to be normally distibuted

Answer 48

Central Limit Theorem

Question 49

Range of values consistent with data from a study A guide to the variability in the study

Answer 49

Confidence intervals

Question 50

Distribution where the mean, median and mode would have the same values

Answer 50

Bell shaped curve | Normal distribution

Question 51

Normal type of distribution MCL? MOS?

Answer 51

Arithmetic mean | Standard deviation

Question 52

Asymmetrical or skewed type of distribution MCL? MOS?

Answer 52

Median | Range or interquartile range

Question 53

Exponential or logarithmic type of distribution MCL? MOS?

Answer 53

Geometric mean | Geometric standard