Statistics

Question 1

What kind of data uses whole numbers that are mutually exclusive (e.g. infected vs. not infected)

Answer 1

Discrete

Question 2

What kind of data contains information that can be measured on a continuum or scale, have numeric values between the minimum and maximum values and requires a process of measuring rather than counting?

Answer 2

Continuous

Question 3

Simplest or crudest level of measurement. Categories are used to classify observations into mutually exclusive groups or classes

Answer 3

Nominal scale

Question 4

observations are ranked so that each category is distinct and stands in some definite relationship to each of the other categories.

Answer 4

Ordinal scale

Question 5

When data meet all the requirements for ordinal data and the exact distance between any two observations on the scale is known.

Answer 5

Interval Scale

Question 6

sum of values / # of observations

Answer 6

mean

Question 7

the point at which 50% of the values fall below a middle value and 50% of the values occur above the middle value

Answer 7

Median

Question 8

middle value of an odd numbered set of values

Answer 8

median

Question 9

(2 middle values) / 2 in an even numbered set of values

Answer 9

median

Question 10

Observation that occurs most frequently in a set of data

Answer 10

mode

Question 11

1 SD will contain ___% of the measurements

Answer 11

68%

Question 12

2 SD will contain ___% of the measurements

Answer 12

95%

Question 13

3 SD will contain __% of the measurements

Answer 13

> 99.7%

Question 14

Positive Skew means

Answer 14

Mean > Median

Question 15

Normal distribution means

Answer 15

mean, median and mode are equal

Question 16

Negative skew means

Answer 16

Mean < Median

Question 17

Mesokurtosis

Answer 17

Normal bell shape

Question 18

Leptokurtosis

Answer 18

More peaked shape curve

Question 19

Platykurtosis

Answer 19

flatter shaped curve

Question 20

Basic formula for all rates

Answer 20

(X/Y) * K

Question 21

Indicates the risk of disease in a population over a period of time

Answer 21

Incidence

Question 22

K (constant used to transform equations into uniform quantity)

Answer 22

made so the smallest calculated rate is at least 1 number to the left of the decimal

Question 23

Incidence Rate

Answer 23

Equals the number of new cases of a disease for a specified time period

Question 24

Prevalence Rate

Answer 24

Equals the number of existing cases of disease from a specified interval or point in time

Question 25

The proportion of persons in a population with a particular disease or attribute at specific point in time.

Answer 25

Prevalence

Question 26

summary measure that compares HAI rates over time among one or more groups of patients to that of a standard population

Answer 26

Standardized Infection Ratio (SIR)

Question 27

Proportion of persons at risk who become infected over an entire period of exposure

Answer 27

Attack Rate

Question 28

Attack Rate

Answer 28

of new cases / population at risk (for same time period) * 100

Question 29

Measure of the frequency of death in a defined population, during a specified time (usually a year)

Answer 29

Mortality Rate

Question 30

Mortality Rate

Answer 30

dead / estimated population * K ``` K = 1,000 for crude rates K = 100,000 for cause specific ```

Question 31

Difference in rate of a condition between an exposed population and an unexposed population.

Answer 31

Attributable risk

Question 32

Attributable Risk Formula

Answer 32

Incidence in exposed - incidence in unexposed

Question 33

Odds ratio formula

Answer 33

Draw Table and (A*D)/(B*C)

Question 34

Probability of not having a disease given a negative screening test result in the screened population

Answer 34

Negative predictive value

Question 35

Probability of having the disease given a positive screening test result in the screened population

Answer 35

Positive predictive value

Question 36

The higher prevalence of the disease, PPV____________ & NPV ________________

Answer 36

PPV increases, NPV decreases

Question 37

Relative risk equation

Answer 37

Draw table | A/R1) / (C/R2

Question 38

If R (relative risk) equals 1....

Answer 38

There is no significant association

Question 39

If R < 1

Answer 39

There is a negative association

Question 40

If R > 1...

Answer 40

There is a positive association

Question 41

The probability of committing a Type I error is referred to as

Answer 41

Significance level

Question 42

This type of error means rejecting the null hypothesis when it is true and attributing significance where there is none

Answer 42

type 1 (alpha)

Question 43

This type of error means accepting the null hypothesis when it is false or not attributing significance when it exists

Answer 43

Type II (Beta)

Question 44

You can reduce a Type I error by...

Answer 44

Decreasing the length of rejection area, keep alpha level very small (0.05, 0.01)

Question 45

You can reduce Type II errors by

Answer 45

Increasing the sampling size

Question 46

The p value in statistical test results indicates

Answer 46

The probability of having committed a Type 1 error

Question 47

What parametric test type test that the means of two sample groups are not different for a sample size >30 with normal distribution?

Answer 47

Z test

Question 48

What parametric test is used with the sample size is < 30?

Answer 48

T test

Question 49

T/F: Non-parametric test (such as Chi-square) make no assumptions about distribution of population values.

Answer 49

True

Question 50

The probability that a test correctly identifies patients without disease as negative

Answer 50

Specificity

Question 51

The probability that a test correctly identifies as positive patients who have the disease

Answer 51

sensitivity

Question 52

Sensitivity Equation

Answer 52

TN/(TN + FP)

Question 53

Specificity Equation

Answer 53

TP/(TP+FN)

Question 54

Chi-square Equation

Answer 54

(O-E)^2/E

Question 55

This non-parametric type of test is used for medium to large samples and tests the association between two classifications of a set of counts or frequencies.

Answer 55

Chi-square

Question 56

This non-parametric test is used in place of the chi-square when the sample size number is <20

Answer 56

Fisher's Exact

Question 57

The _____ of a test is its ability of a test detect a specified difference (e.g. the probability of rejecting the null hypothesis when it is false)

Answer 57

Power

Question 58

Power of a hypothesis is affected by these 3 factors

Answer 58

1. sample size: Bigger sample size=greater the power 2. Significance level: higher significance = higher the power 3. The greater the difference between the "true" value parameter and the value specified in the null hypothesis, greater the power of a test.

Question 59

What kind of graph shows a frequency distribution with values of the variable on the x-axis & the number of observations on the y-axis; data points are plotted at the midpoints of the intervals and are connected with a straight line?

Answer 59

Frequency polygon

Question 60

Difference in rate of a condition between an exposed population and an unexposed population

Answer 60

attributable risk

Question 61

The proportion of cases attributable (and avoidable) to this exposure in relation to all cases.

Answer 61

Attributable Risk Percent (ARP)

Question 62

Attributable Risk Percent Calculation

Answer 62

(relative risk - 1) + relative risk

Question 63

Precision of the relative risk is related to...

Answer 63

the power of a study.

Question 64

this type of chart uses calculated upper & lower limits over time

Answer 64

control charts

Question 65

this type of chart is useful in IC because there can be more than one error per patient taken into account

Answer 65

U Charts

Question 66

This type of chart provide a range of expected variation about a mean and the upper & lower limits beyond which the process is considered out of control

Answer 66

control charts

Question 67

This type of chart is useful in conveying changes in rates over time & identifying points in time when rates are outside the expected range

Answer 67

control charts