Quantitive analysis

Question 1

why is statistics important?

Answer 1

• way to describe and measure biology
• allows us to estimate an unknown quantity using our sample
• test hypotheses

Question 2

is stats math?

Answer 2

kinda? helps us to define what we know, how we know it and how strong the evidence is

Question 3

what do we use descriptive stats for

Answer 3

summarize and describe the data
describe patterns
tables, graphs and charts
- the first step of making inferences

Question 4

what are the 4 types of descriptions of data and their two categories

Answer 4

Categorical
1. nominal
2. ordinal

continuous
1. interval
2. ratio

Question 5

What is nominal data?

Answer 5

• at type of categorical data
  1. non - ordered categories
• sex
• blood type etc

Question 6

what is ordinal data ?

Answer 6

type of categorical data
- ordered categories
eg: house hold income - lowest to highest
eg: age

Question 7

how do we display nominal data?

Answer 7

• frequency tables
• bar graphs

Question 8

how do we display/describe continuous data?

Answer 8

1. frequency table
2. histogram
3. parameters - mean, median etc

Question 9

what is a frequency table?

Answer 9

Create artificial groups and report the frequency
* e.g. age
* This is not very informative and throws out information

Question 10

what does a histogram show?

Answer 10

the shape of the data,

Question 11

how to describe continuous variables?

Answer 11

1. when measuring central tendency
   a)mean
   b) media
   c)mode
2. measuring of variability or spread
   a)range
   b)percentiles
   c) variance/standard deviation

Question 12

what is a central tendency?

Answer 12

the average distribution.continuous variable
summarizes the data with a single value

Question 13

what can the mean be distorted by?

Answer 13

outliers

Question 14

what is the median?

Answer 14

middle of data
order from smallest to largest and average two middle points

Question 15

what is the mode?

Answer 15

number that occurs most often in the data
can be more than 1
not impacted by outliers

Question 16

when to use mode, median and mean

Answer 16

mode - rare
mean - if your sample is normal - bell
median - if your sample is skewed

Question 17

what is the range?

Answer 17

smallest to largest values

Question 18

what are the percentiles? -hard

Answer 18

• a measure of the dispersion for one variable that indicates the % of cases at or below a score or point
  eg: the median is the 50th percentile
  eg: 25th percentile is the value at which 25% of the distribution have that value or a lower one
  often report quartiles - 25th, 50th, 75th

Question 19

what is standard deviation/variance?

Answer 19

• the measure of dispersion for one variable that indicates an “average distance” between the values and the mean

Question 20

what is generally used to show continuous data visually?

Answer 20

boxplots

Question 21

What do boxplots show? - parts of it

Answer 21

• the median
• the IQR - intervals q1 q2 etc
• the range or the outliers

Question 22

if the median is the centre of a boxplot what does it mean

Answer 22

that you have a bell-shaped curve

Question 23

what can boxplot diagrams be used for?

Answer 23

• to compare different groups

Question 24

what are the types of prevalence?

Answer 24

• point prev
• period prev
• lifetime prev

Question 25

what is incidence density/ rate

Answer 25

the number of new cases in a given time period divided by total person-time of follow-up (sum) USed for longitudinal cohort studies - each person contributes time based upon how long they were followed -

Question 26

what happens when individuals are censored in data ?

Answer 26

we exclude any data on them that was gathered after the censoring point, if any

Question 27

what is the unit for incidence density

Answer 27

generally per 100 person-years because you times the number you get by 100

Question 28

what does mortality rate show?

Answer 28

- how many people die from a disease in a given time

Question 29

what does case fatality rate mean

Answer 29

CFR = the proportion of people WITH the disease who die within a given time, again usually one year

Question 30

what is a issue with MR's and CFR's? `

Answer 30

we do not know if the number is high or low except if comparing to other disorders - do not always know how many people have the disorder One way around this issue is to look at death rates for a specific disorder in relation to deaths from all causes...

Question 31

What is the proportional Mortality Rate? PMR

Answer 31

the number of deaths due to a disorder in a given time divided by ........... number of deaths from all disorders - makes sense only when we compare the PMR from one disorder to another disorders PMR

Question 32

How can the PMR for a disease increase over time? 2 reasons

Answer 32

1. more people may be contracting and dying from the disorder 2. fewer people may be dying from other causes

Question 33

What is the Standardized Mortality Rate?

Answer 33

the ratio of the number of observed deaths from a given cause in a given time to the expected number of deaths - this measure does not have to be compared to others

Question 34

how do we interpret SMRs? Standardized mortality rates

Answer 34

- an SMR less than 1 = people with the disorder are dying lower than the expected rate - an SMR more than 1 = higher than the expected rate

Question 35

when does using the general population not make sense as a reference group?

Answer 35

when comparing groups with different age structures - need to use - age-standardized mortality rates

Question 36

what do measures of impact find? m

Answer 36

how dangerous the disease is - relative risk or odds

Question 37

what is the relative risk

Answer 37

the ratio of... 1. the risk of death in the exposed group - a divided by a+b 2. the risk of death in the unexposed group - c divided by c+d relative risk is the ratio of these two risks exposed risk divided by unexposed risk

Question 38

what are the limitations of relative risk?

Answer 38

the relative risk is the same regardless of prevalence of the disorder

Question 39

what is relative risk reduction RRR

Answer 39

improvement as a percent relative to the comparison group risk (treatment) - risk (control) divided by............ risk (control)

Question 40

Absolute risk reduction ARR

Answer 40

- decrease in the risk of the treatment group compared to the control group risk treatment - risk control

Question 41

What is the number needed to treat? NNT

Answer 41

the number of people who need to be treated to have one additional positive outcome NNT = 1/0.1 = 10 eg: need to treat 10 people for one cure

Question 42

What is the odds ratio?

Answer 42

this is used in case-control studies to assess the relationship between the exposure and the disease - the ratio of the odds of exposure among the cases compared to the odds of exposure amount the controls

Question 43

what does PICO stand for?

Answer 43

population intervention comparison outcome