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hsci 207 research > Quantitive analysis > Flashcards

Quantitive analysis Flashcards

1
Q

why is statistics important?

A
  • way to describe and measure biology
  • allows us to estimate an unknown quantity using our sample
  • test hypotheses
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2
Q

is stats math?

A

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

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3
Q

what do we use descriptive stats for

A

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

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4
Q

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

A

Categorical
1. nominal
2. ordinal

continuous
1. interval
2. ratio

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5
Q

What is nominal data?

A
  • at type of categorical data
    1. non - ordered categories
  • sex
  • blood type etc
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6
Q

what is ordinal data ?

A

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

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7
Q

how do we display nominal data?

A
  • frequency tables
  • bar graphs
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8
Q

how do we display/describe continuous data?

A
  1. frequency table
  2. histogram
  3. parameters - mean, median etc
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9
Q

what is a frequency table?

A

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

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10
Q

what does a histogram show?

A

the shape of the data,

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11
Q

how to describe continuous variables?

A
  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
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12
Q

what is a central tendency?

A

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

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13
Q

what can the mean be distorted by?

A

outliers

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14
Q

what is the median?

A

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

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15
Q

what is the mode?

A

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

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16
Q

when to use mode, median and mean

A

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

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17
Q

what is the range?

A

smallest to largest values

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18
Q

what are the percentiles? -hard

A
  • 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
19
Q

what is standard deviation/variance?

A
  • the measure of dispersion for one variable that indicates an “average distance” between the values and the mean
20
Q

what is generally used to show continuous data visually?

A

boxplots

21
Q

What do boxplots show? - parts of it

A
  • the median
  • the IQR - intervals q1 q2 etc
  • the range or the outliers
22
Q

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

A

that you have a bell-shaped curve

23
Q

what can boxplot diagrams be used for?

A
  • to compare different groups
24
Q

what are the types of prevalence?

A
  • point prev
  • period prev
  • lifetime prev
25
Q

what is incidence density/ rate

A

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 -

26
Q

what happens when individuals are censored in data ?

A

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

27
Q

what is the unit for incidence density

A

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

28
Q

what does mortality rate show?

A
  • how many people die from a disease in a given time
29
Q

what does case fatality rate mean

A

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

30
Q

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

A

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…

31
Q

What is the proportional Mortality Rate? PMR

A

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
32
Q

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

A
  1. more people may be contracting and dying from the disorder
  2. fewer people may be dying from other causes
33
Q

What is the Standardized Mortality Rate?

A

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

34
Q

how do we interpret SMRs? Standardized mortality rates

A
  • 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
35
Q

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

A

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

36
Q

what do measures of impact find? m

A

how dangerous the disease is
- relative risk or odds

37
Q

what is the relative risk

A

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

38
Q

what are the limitations of relative risk?

A

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

39
Q

what is relative risk reduction RRR

A

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

40
Q

Absolute risk reduction ARR

A
  • decrease in the risk of the treatment group compared to the control group
    risk treatment - risk control
41
Q

What is the number needed to treat? NNT

A

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

42
Q

What is the odds ratio?

A

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

43
Q

what does PICO stand for?

A

population
intervention
comparison
outcome

hsci 207 research (12 decks)

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