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RESS Year 2 > RESS - Ebook > Flashcards

RESS - Ebook Flashcards

1
Q

What type of data do bar charts use?

A

Categorical (ordinal and nominal) and Numerical discrete

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2
Q

What type of data do pie charts use?

A

Categorical (ordinal and nominal)

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3
Q

What type of data do histograms use?

A

Numerical Continuous

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4
Q

In a histogram what does the area of the bar and the height of the bar mean?

A

Area: Frequency
Height: Frequency/Class width

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5
Q

What is standard deviation?

A

Average distance of all the points from the MEAN!

Larger the SD- bigger distribution of data

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6
Q

With what type of data is SD used

A

Normally distributed

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7
Q

What is IQR?

A

Q1 - Median - Q3

Between Q1 and Q3 is the IQR which is where 50% of the distribution lies

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8
Q

With what type of data is IQR used?

A

Skewed data

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9
Q

Define Incidence

A

Incidence is the number of new cases over a specific time period
Number of new cases/ Number at risk

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10
Q

Define Prevalence

A

Prevalence is the number of cases of disease at a particular time point
Number of people with a disease/ number of people in a population

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11
Q

Define Mortality

A

Mortality is the number of people dying from a disease

Number of people who die from a disease/Number of people who die in general

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12
Q

Define Case Fatality

A

number dying in period from disease / number with the disease in period

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13
Q

What is risk?

A

Synonymous with probability

Number of new cases/ Number at risk

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14
Q

What is a risk ratio?

A

Shows relative risk in an exposed and unexposed group

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15
Q

When is risk ratio used?

A

Cohort studies to show relative risk!

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16
Q

What is odds?

A

Number of time an event occurs / Number of time it doesn’t occur

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17
Q

What is odds ratio?

A

Shows relative risk

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18
Q

When is odds ratio used?

A

Case control studies and RCT to show relative risk!

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19
Q

What two things can determine relative risk?

A

Odds ratio (RCT and case control) and Risk ratio (cohort studies)

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20
Q

What does a RR of 1 show?

A

means risk in exposed = risk in unexposed so no benefit or harm

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21
Q

What does RR <1 show?

A

means risk in exposed < risk in unexposed exposure is protective

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22
Q

What does RR >1 show?

A

means risk in exposed > risk in unexposed exposure is harmful

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23
Q

What does Gaussian distribution show?

A

Normal distribution in the shape of a bell curve

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24
Q

What are features of normal distribution?

A

Values symmetric around the mean
Greatest frequency is at the mean
Normal distribution is symmetric around the mean median and mode

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25
Q

What are features of a normal distribution curve?

A

SD is how broad the bell is
Area under the curve is 1
Mean = 0
SD= 1

26
Q

How do you make probability statements about a variable using a distribution curve?

A

Transform the distribution curve to a standard normal distribution curve

27
Q

What is standard error?

A

Used to calculate confidence intervals of the mean (Standard deviation needs to be known to calculate standard error)
(Is a measure of the precision of the sample mean)
The larger the sample size the lower the standard error

28
Q

What is a confidence interval

A

A range of feasible values that the true (mean) value is believed to be within (usually 95% probability)

29
Q

What does it mean if a confidence interval crosses 0?

A

If a confidence interval crosses this is not statistically significant as the effect of the variable could be 0

30
Q

How is the SE and thus confidence interval calculated if you have known SD?

A

Known SD if >200 samples

Confidence interval calculated using critical values from standard normal distribution

31
Q

How is the SE and thus confidence interval calculated if you have estimated SD?

A

Estimated if sample size <200

Confidence interval calculated using students t distribution

32
Q

What has a wider range 90% CI or 95%

A

95% (as to be 95% sure the ranges will be wider)

33
Q

What is a null hypothesis?

A

Opposite to hypothesis; assumes nothing happens

34
Q

What is an alternative hypothesis?

A

Has two possible outcomes e.g. drug will decrease hypertension or increase hypertension

35
Q

What assumptions are necessary for the test statistic?

A

1 - The variable; change in bp has to be normally distributed
2- The samples are independence i.e. from different patients

36
Q

What is the p value?

A

The probability that the null hypothesis is true

Lower the P value the less likely the null hypothesis is true

37
Q

When is the p value statistically significant?

A

When it is <0.005

38
Q

Are confidence intervals adequate for hypothesis testing?

A

Yes

39
Q

What is parsons correlation coefficient?

A

r

Measure of linear correlation between two numerical values

40
Q

R values =0, >0, <0, 1 and - 1

A 
=0 Linear relationship
>0 Positive correlation
<0 Negative correlation
1 perfect correlation
-1 perfect negative correlation
41
Q

What value of correlation is treated with suspicion

A

<0.7

42
Q

When should pearsons coefficient not be used?

A

No linear relationship
Outliers
Subgroups i.e. not numeric
One or both variables are not normally distributed

43
Q

When pearsons coefficient can’t be used what is used instead?

A

Speerman rank correlation

44
Q

When is superman rank correlation used?

A

Ordinal data
Small sample size
Data not normally distributed

45
Q

In linear regression analysis what is on the X and Y axis

A

X axis: independent variable

Y axis: Dependent variable

46
Q

What requirements are needed for regression analysis?

A

Linear relationship

Normally distributed

47
Q

What is the chi squared test?

A

Association between two categorical variables

48
Q

What does the chi squared test compare?

A

Contingency tables from; results observed and results expected if null hypothesis was true

49
Q

What conditions are required fro chi squared test?

A

4 cells should be more than 1

Three of these should be more than 5

50
Q

If conditions are not met for a chi squared test what else can be used?

A

Fishers exact test

51
Q

Sensitivity

A

How well a test detects a condition

52
Q

Specificity

A

How well a test correctly excludes those without the condition

53
Q

Positive predictive value

A

Probability someone has the condition if they test positive

54
Q

Negative predictive value

A

Probability someone doesn’t have the condition if they test negative

55
Q

Failure Event

A

The time a person leaves a study is known

56
Q

Censory

A

Leaving a study before the event occurs or enters late

57
Q

Left Censory

A

Disease present before the entered (not sure what happened before they entered)

58
Q

Right censory

A

People in the study did not reach a failure before the end (i.e for HIV drug an individual left country or died from non HIV related cause)

59
Q

Survival Function

A

Chance of survival until a certain time

60
Q

Hazard Function

A

Chance of an instantaneous failure

61
Q

Kapplan meir plot

A

Shows survival as a series of steps

It steps down every time a failure is observed

RESS Year 2 (3 decks)

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