Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

FRACP NOSH 2020 > Statistics > Flashcards

Statistics Flashcards

1
Q

What indicates if a test is reliable?

A

If it is repeated again and again and gets the same result

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What does it mean if a test is valid?

A

If it meets the requirements of the scientific study

e.g. randomisation, blinding

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What type of data is nominal?

A

categorical, with no ranking

e.g. gender, blood group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What type of data is ordinal?

A

categorical with ranking

e.g. preference scale

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what type of data is discrete?

A

numerical data which is in whole numbers

e.g. number of people

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the variance of a sample? How is it calculated?

A

A measure of dispersion of sample

Average of squared differences from the mean

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the relationship between variance and SD?

A

SD = square root of variance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What assumptions must be made with parametric data?

A

Continuous data

Population data is normally distributed

Sample and source population have same SD/variance e.g. spread

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

When are non-parametric tests more appropriate than parametric?

A

When data is not continuous (e.g. ordinal, nominal)

When distribution of population is not known

Small sample size -> less affected by outliers, uses median rather than mean. RANKS data

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the central limit theorem?

A

In a skewed population, sample becomes more “normal” in shape as n increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the parametric test used to compare 2 independant groups?

What is the non-parametric equivalent?

A

T-test

Wilcoxon rank sum test

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the parametric test used to compare paired observations?

What is the non-parametric equivalent?

A

T-test for paired

Wilcoxon signed rank test

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the parametric test used to compare several groups?

What is the non-parametric equivalent?

A

ANOVA

Kruskal Wallis test

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the parametric test used to find linear relationship between 2 variables e.g. BP and sleep duration?

What is the non-parametric equivalent?

A

Pearson’s correlation

Spearman’s Rank correlation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the non-parametric test used to test association between 2 qualitative variables e.g. gender, smoking status?

Which one for sample size
>50?
<50?

A

Chi squared

> 50 -> chi squared

<50 -> Fisher’s exact

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the difference between t-statistic and z-statistic?

A

T = sample with unknown SD

Z = known SD

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is a Type 1 error?

How is it minimised?

A

False positive

i.e. wrongly rejecting null hypothesis
Avoid by setting p-value low enough

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is a Type 2 error?

How is it minimised?

A

False negative

i.e. wrongly accepting null hypothesis
Avoid by having enough POWER

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is “power” of a study?

i.e. what does 80% power in a study mean?

A

The ability of a study to demonstrate a statistically significant association

80% power = study has 80% chance of ending with a p-value <0.05

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is “power” of a study?

i.e. what does 80% power in a study mean?

A

The ability of a study to demonstrate a statistically significant association

80% power = study has 80% chance of ending with a p-value <0.05

21
Q

What would changing your p-value cut-off from 0.05 to 0.01 do to the power of a study?

A

Decrease it

Smaller p-value requires more power

22
Q

How can power be increased in a study design?

A

Increase sample size

Increase p-value

Increase effect size

23
Q

What does a 95% confidence interval indicate?

A

we are 95% confident that true population mean occurs within this interval

24
Q

What error is more likely with post-hoc analyses?

A

Type 1 error

25
Q

What is the familywise error rate?

What is the Bonferroni correction?

A

Cumulative Type 1 error

e.g. if testing 3 hypotheses, need to calculate 0.95 x 0.95 x 0.95

Bonferroni correction compensates for this by fixing p-value across tests

26
Q

WHich of these measures is not affected by prevalence of an event?

ARR
NNT
RR

A

RR

27
Q

What is the difference between odds of an event and probability of an event?

A

Odds = no. of events / no. of NON-events

Probability = no. of events / TOTAL events

28
Q

What is the log rank test used for?

A

To compare 2 survival curves

29
Q

Which study design is best for rare disease?

Which study design is best for rare exposures?

A

Rare disease - case-control

Rare exposure - cohort

30
Q

What is the rationale for randomisation in RCTs?

A

To reduce confounding

Reduces selection bias

31
Q

What is the rationale for blinding?

A

To reduce information (observe) bias

32
Q

What kind of bias does non-random sampling lead to?

A

Selection bias

33
Q

What kind of bias can occur if investigators know which intervention the next participant will receive

A

Allocation / channelling bias

34
Q

What is ascertainment bias?

A

When data is collected in a way such that some members of population are less likely to be included

e.g. requiring a doctor’s visit to get Alzheimer’s diagnosis

35
Q

What is information bias?

A

Systematic difference in way information is collected / recorded

36
Q

Which types of studies are liable to recall bias?

A

Where self-reporting occurs e.g. case control

37
Q

What is the Hawthorne effect?

A

Participants report improvement if they know they are on the drug/being observed

38
Q

what is the Halo effect?

A

error in reasoning where impression is formed due to a single trait

39
Q

What are trials of nutrition or exercise liable to (with bias)?

A

Performance bias

may inflate estimated effect of intervention, with subjective outcomes

40
Q

What is length time bias?

A

Diseases with long duration are more likely to be included in screening, and are less aggressive

e.g. slower-growing cancers are picked up on screening and tend towards better prognosis

41
Q

What is lead time bias?

A

Occurs when a disease is diagnosed earlier, but it actually has no impact on outcome of disease. However it appears like there is prolonged survival

42
Q

What is the aim of intention to treat analysis?

A

To minimise selection bias

Under-estimates effect

43
Q

What is another name for True positive rate?

A

Sensitivity

44
Q

What is another name for True negative rate?

A

Specificity

45
Q

Which of these are affected by prevalence of disease?

Sens
Spec
NPV
PPV

A

NPV -> increasing prevalence decreases NPV

PPV -> increasing prevalence increases PPV

46
Q

What is the purpose of Phase 1 trials?

A

Focus on pharmacology

  • in small number of healthy subjects
  • dose-finding, dosing schedule
47
Q

What is the purpose of Phase 2 trials?

A

Focus on safety

- usually in subjects with disease, but small number

48
Q

What is the purpose of Phase 3 trials?

A

Focus on efficacy

- large numbers of patients with disease

49
Q

What is the purpose of Phase 4 trials?

A

Focus on long-term effects

- post-marketing

FRACP NOSH 2020 (18 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions